Situated along the northeastern coast of the island, Ancient Kos emerged as a strategically positioned and culturally dynamic city within the Dodecanese, commanding maritime routes between Asia Minor and the Aegean region. Archaeological evidence indicates an organized city plan established in the fourth century BCE following the earthquake of circa 411 BCE and the subsequent unification of the island’s earlier poleis. The city was constructed on a rectilinear Hippodamian grid, characterized by colonnaded streets (cardines and decumani), public baths, temples, and port installations.

Excavations conducted since the Italian occupation in the early 20th century CE—most notably by Luigi Morricone and later Greek archaeological missions—have revealed a stratified urban sequence representing Classical, Hellenistic, Roman, and Byzantine phases. Among the most prominent remains are the Hellenistic agora, one of the largest in the Aegean, which functioned as the civic and commercial heart of the city; the Sanctuary of Heracles and the Altar of Dionysus; the Roman Odeon and gymnasium; and an extensive network of mosaicked houses reflecting elite domestic architecture.

The Asclepeion, situated approximately 3 kilometers southwest of the main city, functioned as both a healing sanctuary and a medical training center, affirming Kos’s association with Hippocrates and the development of rational medicine. The urban fabric, its harbor infrastructure, and monumental architecture collectively illustrate Kos’s integration into the Hellenistic koine and its later transformation under Roman administration.

Modern archaeological zones—particularly the Western Archaeological Zone, the Ancient Agora, and the harbor area—demonstrate the city’s continuity and adaptation across epochs. These remains, coupled with inscriptions, sculpture, and architectural fragments housed in the Archaeological Museum of Kos, provide a coherent material and spatial record of an Aegean polis that bridged Greek, Egyptian, and Anatolian cultural spheres.

circa 4000 BCE- Modern Period

Origins and Founding Myths
The island of Kos is enveloped in a rich tapestry of myth, legend, and early traditions that seek to explain its name, its first inhabitants, its sacred geography, and the divine or heroic figures associated with its foundation. These founding myths do not always align cleanly with archaeological or historical data, yet they have shaped Kos’s identity from antiquity.

One widespread legend holds that the eponymous founder‑king of the island was Merops (sometimes “Meropas”), from whom the name Meropian Kos is said to derive. Under this version, “Meropes” refers to the people of Merops or to his dynasty. The Homeric tradition also acknowledges Kos: in the Iliad, a contingent from Kos under Eurypylus participates in the Trojan War fought between ancient Troy and Greek States under Agamemnon.

Another myth locates Kos’s origins in divine genealogy. According to these tales, the gods Coeus and Phoebe (titans in Greek myth) are involved: Coeus is sometimes named as the first inhabitant, or progenitor of the line that includes Leto, mother of Apollo and Artemis. In some accounts Leto herself is said to have been born on Kos. These associations underscore the sanctity of the land in mythic memory.

The island’s name has several mythical explanations. One claims it comes from Koos, a daughter of King Meropas; another that it derives from a Titan named Kinnos, or from Koios. In some traditions Kos is named after Koos the queen’s daughter, while alternate etymologies suggest older roots in pre‑Greek or non‑Hellenic peoples—such as the Pelasgoi or Leleges—who are sometimes said to have been the island’s first settlers.

Myths also involve giants and battles between divine or heroic forces. One tradition holds that the island was once inhabited by giants, offspring of sky and earth. After being defeated in the struggle with the Olympian gods, some giants fled to Kos. One version says that Poseidon cut off a piece of the land and hurled it at the giant Polibotes during their struggle, thereby killing him. Other giants such as Koios, Phoebe, and Kinnos are said to have fled trauma or defeat to Kos.

The arrival of human settlers is also embedded in myth. Some narratives describe early colonists from Epidaurus—Dorians—settling the island. The Epidaurian settlers are sometimes linked with the introduction or development of the cult of Asclepius (Aesculapius), reflecting the later importance of the island’s medical sanctuary, the Asclepieion.

Heroic legends amplify Kos’s sacred landscape. Heracles (Hercules) is sometimes portrayed as having visited or stayed on Kos, or as a founding hero of sorts. The cult of Heracles on Kos features in ancient coins and local cultic practices: for example, coins from Kos display the head of Heracles, and his sanctuary was placed in a prominent location in the city. These tales connect the heroic age with the civic and religious life of Kos.

While these myths are ancient, they often served practical functions: legitimizing political institutions (by claiming descent from divine or heroic lineages), explaining the names of cities and places, endorsing sanctuaries, and giving moral or religious meaning to customs. Archaeology shows habitation on Kos from at least the Neolithic and Bronze Age (including Mycenaean period settlement at Serayia), and some of the mythic claims—early settlers, powerful visitors, cults to healing deities—correspond loosely with those long history elements.

Archaic Period
The early history of Kos remains only partially documented. During the Archaic Period it was a member of a religious-political amphictyonic league known as the Doric Hexapolis, which included Lindos, Kamiros, Ialysos, Knidos, and Halicarnassus. At the close of the sixth century BCE, the island came under the sway of the Achaemenid Empire. After the Greek victory at the Battle of Mycale in 479 BCE, Kos participated in a rebellion against Persian control. Archaeological evidence from this period indicates the presence of a small shrine dedicated to Hemera and Helios, reflecting cultic practices associated with day and sun deities.

Classical Era
Throughout the Greco-Persian conflicts, the rule of Kos alternated; on occasion it was governed by tyrants appointed by the Persians, yet much of the time it appears to have been under oligarchic rule. In the fifth century BCE, Kos became a member of the Delian League. Following Rhodes’ revolt, between 411 and 407 BCE it served as the principal Athenian station in the southeastern Aegean. In 366 BCE a democratic form of government was established, and the political centre of the island shifted from Astypalaea (situated at the island’s western extremity near what is today the village of Kefalos) to a newly established city, Cos, which was laid out according to the grid plan attributed to Hippodamus of Miletus. During the Social War (357-355 BCE), Kos aided in the weakening of Athenian influence; subsequently it briefly came under the dominion of Mausolus of Caria. Trade and cultural production flourished during this era. Proximity to eastern trading routes enabled the importation of silk thread; literary sources assert that women on Kos engaged in silk weaving. The presence of workshops, possibly staffed by female slaves, attests to a textile industry of some scale.

Hellenistic Period
In the period following the death of Alexander the Great, Kos was seized by Ptolemy I Soter from Antigonus I Monophthalmus, and was integrated into the Ptolemaic realm. Under Hellenistic rule, the island experienced its greatest prosperity. The Ptolemies valued Kos as a maritime stronghold in the Aegean, and the island became a provincial extension of the Alexandrian Museum in terms of learning and culture. Princes of the Ptolemaic dynasty often received part of their education here.

Kos was also renowned for its medical school, although the attribution of its foundation to Hippocrates during the Classical age remains unsupported by conclusive evidence. Among noted scholars resident there was the Hellenistic poet-scholar Philitas. Despite Ptolemaic sovereignty, Kos maintained a significant degree of political autonomy: decrees from the third century BCE indicate that local citizens’ assemblies and magistrates—such as the prostates and exegetes—presided over internal legislation and justice.

Economic prosperity during this era is visible in material remains: the Asclepeion was expanded; a theatre was constructed; markets with multiple stoas were built; there arose richly decorated houses and extensive fortification works. In 240 BCE, under guarantees from rulers such as Ziaelas of Bithynia, Seleucus II Callinicus, and Ptolemy III Euergetes, the Asclepeion of Kos was formally designated as an asylum—a status that increased its attraction to pilgrims and merchants.

Kos also developed a strong reputation for judicial fairness and arbitration. The city was regularly called upon to send judges to resolve disputes among other Greek cities. For instance, between 310 and 300 BCE, Kos arbitrated the conflict between Klazomenai and Teos; also it provided legal frameworks for the synoecism of Teos and Lebedus. Inscriptions show that in the following centuries its jurisdiction was sought in Naxos, Thasos, Erythrae, Mytilene, and Telos. In one recorded case at Telos, jurists from Kos resolved internal political crimes by allowing offenders to pay fines and make amends via public sacrifices and temple repairs.

Geographically strategic and well fortified, Kos played a prominent role in Aegean trade. It was famous for its wines. Under the Ptolemies and earlier, the city burgeoned into a major centre in the region. Ancient authors like Strabo and Diodorus Siculus describe the city as a strong port. There are traditions—quoted by Josephus through Strabo—that Cleopatra deposited gold there and that Mithridates I of the Bosporus was sent to retrieve it. Additionally, Herod (King of Judaea) is said to have provided funds for athletic prize-winners on Kos, and a statue was erected in honour of his son, Herod the Tetrarch. According to Christian scripture (Acts 21:1), Paul visited the island briefly.

Roman Period
During the Roman era, Kos generally enjoyed peace, interrupted only by occasional pirate raids and earthquakes. In 53 CE the island was granted the status of a free city, which conferred certain rights and privileges under Roman governance. A provincial library was established; several individuals contributed—among them Gaius Stertinius Xenophon, a Koan physician who served as doctor to emperors Tiberius, Claudius, and Nero, is known to have financed part of this institution.

Under Roman Imperial patronage, local institutions such as the gymnasiarch’s office received endowments from foreign rulers. An inscription dating to approximately 14 BCE honours Gaius Julius Herodes, who had adopted Roman naming conventions, possibly related to his contributions or financial support for such offices.

Byzantine Era
After the consolidation of Roman authority into the Eastern Roman sphere (Byzantine Empire), the Church became an important institution on Kos. Its bishopric was subordinate to the metropolitan see of Rhodes. Bishops from Kos took part in significant early ecumenical councils: Meliphron in the First Council of Nicaea (325 CE), Iulianus at the synod preceding Chalcedon (451 CE) as legate of Pope Leo I, Georgius in the Third Council of Constantinople (680-681 CE), and Constantinus attending the Photian Council of Constantinople in 879 CE.

Secular political details during this period are less fully documented. From the 8th to 9th centuries the island was administered by a droungarios, a Byzantine naval military office. In later centuries, particularly the 11th and 12th, Kos gained in strategic significance; Nikephoros Melissenos initiated his uprising there, and governance by a member of the Komnenos dynasty (Nikephoros Komnenos) is attested in the mid-12th century CE.

Kos remains today an ecclesiastical metropolis under the direct jurisdiction of the Patriarchate of Constantinople rather than the Church of Greece, and the Catholic Church lists it as a titular see.

Genoese and Hospitaller Periods
Following the 11th century CE, Kos experienced shifts in control, though it formally remained a Byzantine territory for a time. Genoese influence was asserted through a protectorate arrangement; from the 1320s it was nominally under Genoese rule (specifically under Vignolo de Vignoli), and the Knights Hospitaller were granted residence, with the island paying tribute to Genoa. During this era, Turkish corsair raids grew more frequent. Between 1391 and 1396 CE, Yıldırım Bayezid’s forces launched attacks; two towers added to the castle’s fortifications date from this period. In 1455 CE the Ottomans made a serious assault: Hamza Bey besieged and destroyed Andimacheia Castle. The final Hospitaller governor before Ottoman takeover was Piero de Ponte.

Ottoman, Italian, and Modern Era
Kos came under Ottoman control in the mid-15th century cE. It remained under Ottoman rule until the Italo-Turkish War of 1912 CE, when Italy seized the island. The Italians undertook significant building projects, especially after a devastating earthquake on 23 April 1933 CE. Architect Rodolfo Petracco drafted a new plan for the city; the old quarters were set aside as an archaeological park, while new sections were organized into residential, commercial, and administrative zones. During World War II, Kos was held by Italian forces until Italy’s surrender in 1943 CE; subsequently British and German troops fought for control in the Battle of Kos during the Dodecanese Campaign. After German occupation ended in 1945 cE, the United Kingdom administered the island until it was formally ceded to Greece in 1947 CE under the Paris Peace Treaty.

circa 400 BCE

Ancient Agora
The Ancient Agora of Kos, dating to the 4th century BCE, is a multi-layered archaeological site situated in the eastern sector of the modern city, near the harbor. Its historical significance stems from its role as the administrative, commercial, and social heart of Kos following the island's capital relocation in 366 BCE. The visible ruins, largely a result of extensive Italian-led excavations following the devastating 1933 earthquake, reveal a complex stratigraphy representing different construction phases. The original 4th-century construction, utilizing limestone and travertine, gave way to more monumental marble edifices in the 2nd century BCE.

The site, one of the largest excavated agoras in Greece, encompasses not only the central market but also the foundations of sanctuaries dedicated to deities such as Aphrodite and Heracles, a basilica, and sections of the ancient city walls. Significant evidence of Roman-era reconstruction following the 142 CE earthquake and the definitive end of the ancient city after the 469 CE seismic event highlight the island's resilience and subsequent repurposing of its urban space in the Early Christian period. The surviving remnants, including columns, stoa foundations, and mosaic floors, offer critical insights into the urban planning, economic activities, and religious practices of ancient Kos.

circa 400 BCE

Asklepieion Complex
The Asklepieion complex on Kos is a multi-layered archaeological site that developed over several centuries, beginning in the fourth century BCE on a sacred cypress grove dedicated to Apollo and Asclepius. Its tiered construction across three major terraces is a defining feature, designed to maximize the therapeutic potential of the natural landscape. The lowest terrace housed treatment rooms, Roman-era baths, and the impressive Propylon entrance. The middle terrace, accessible via a monumental staircase, was the spiritual and intellectual heart of the complex, containing the oldest altar to Asclepius (mid-fourth century BCE), the priestly residence (abaton), and a third-century BCE Temple of Asclepius.

At the highest level, a large Doric temple dedicated to Asclepius, dating to the second century BCE, dominated the sanctuary, visible from the harbor and demonstrating its panhellenic significance. After its decline due to earthquakes, particularly in the 6th century CE, the complex's stones were extensively repurposed by the Knights Hospitaller for Neratzia Castle, while the site itself was partially occupied by an early Christian church. Excavations by German and Italian archaeologists in the early 20th century CE uncovered the complex, revealing invaluable insights into the synthesis of religious worship, medical practice, and architectural design in ancient Kos.

circa 400 BCE

East Stoa
The east stoa of the agora, 316 meters in length, retains its course and form unaltered throughout all the building phases of the ancient monument. Along its north side, in the the harbour, situated at the rear part of the portico, there were oblong spaces that apparently served as storage facilities of trade goods. In the fourth century BCE their entrance was sealed with metal panels, which were replaced with doors in the second century BCE. During the Imperial Roman times, when commercial activity moved out of the agora, they were widened and divided into three aisles, serving obviously, different purposes.

On the contrary, in the south part of the agora— the spaces of the east stoa maintain the same layout in all of the building phases: they nave a bipartite ground plan, with the east portion further divided into two parts. They probably operated as workshops (i.e. for the production of colour pigments using litharge as raw material), while some of them were also shops.

In a land property adjacent to the area of the altar of Dionysos and the temple of the Attalids, excavation uncovered poor remains from the east stoa, at a depth of 3.5 meters below ground level, now reburied in situ. Parts of the colonnade were revealed, as also two shops and the street, aligned east-west, that proviaed direct access from the secular domestic core of the city to the public space of the agora.

The expropriation of the property by the state opened up the opportunity to create a space for recreation and educational programmes focusing on the ancient agora, the layout which is easily perceived through the simulation of the east stoa by features built of new materials at 1:1 scale at the ground level of the archaeological site. These features render the stylobate with the lower part of the Doric columns, the floor of the stoa, the shops and the street aligned east-west.

circa 323-146 BCE

Ancient Theater of Astypalaia
The Ancient Theater of Astypalaia, located at the site of Palatia near modern Kefalos on the island of Kos, is a Hellenistic-period structure dating to the fourth century BCE. Built during the period when Astypalaia served as the island's capital, the theater's design exemplifies classical Greek architectural principles by utilizing the natural slope of the terrain for its koilon (seating area). Excavated by the Italian Archaeological Mission in 1928 CE, the site retains notable structural elements, including the foundation of its 13-meter stage, the bases of four Doric columns, and the circular orchestra with its central thymele (altar) dedicated to Dionysus. The monument provides valuable insight into the cultural and administrative prominence of ancient Astypalaia, which was a member of the First Athenian League before the capital was relocated to Kos Town in 366 BCE. While only a few rows of the original seating survive, the extant ruins, situated with panoramic views overlooking the Kefalos bay, represent a significant archaeological feature of the ancient city.

circa 323-146 BCE

Sanctuary of Hercules
The attribution of the sanctuary to Herakles is based on epigraphic testimonies and part of a lion-skin from the colossal statue of the mythical hero, presently built into the wall of the Loggia mosque, which were found in the vicinity of the sanctuary. The sanctuary was founded in the late fourth to early third century BCE on a trapezoidal area created for this purpose by relocating the harbour wall further east. A temple was possibly constructed on the site, but no remains have been identified. A stoa on the north side served as the monumental propylon of the sanctuary. In the early second century BCE the temple was built in the form of a simple oikos upon a podium. Access was via a flight of ten steps. A stoa, small parts of the foundation of which are preserved, was added to the west side.

In the first to second century CE, porticoes with rooms were added to the north, south and east sides of the court. After the catastrophic earthquake in 142 CE, repairs were made mainly to the ancillary rooms. Mosaic floors of exquisite art, with representations referring to the cult of Herakles, were laid in some of these. The sanctuary was destroyed by the earthquake of 469 CE, by which period it had perhaps already lost its religious status. Thermae were built upon its ruins, continuing in existence until the seventh century CE. During the Hospitaller period the church of Saint Demetrios was erected on the remnants of the temple. It was demolished in order to uncover the sanctuary in its entirety.

The mythical hero Herakles and his companions were driven ashore by a tempest in the area of Cape Laketeras, Kardamaina, whilst homeward bound after the labour of seizing the girdle of the Amazon Hppolyta. There they clashed with the renowned Koan athlete Antagoras, when they took refuge in his sheepfold, in search of food. The inhabitants of Kos, the Meropes, ran for help and forced Herakles and his companions to flee. In order to protect himself, the hero dressed in women's clothes. Immediately afterwards, having rallied round, they succeeded in counteracting the Meropes. After the victory, Herakles, weanng female attire, married Chalkiope, daughter of King Eurypylos of Kos. She bore him a son, Thessalos, father of Antiphos and Pheidippos, who commanded the 10 ships that Kos, Nisyros, the Calydnian islands and Kasos sent to the Trojan War (Iliad II, 676-679 CE).

circa 220-180 BCE

Sanctuary of Aphrodite
The Sanctuary of Aphrodite, located within the Eastern Archaeological Area of Kos Town, is an important example of a Hellenistic religious structure that was later built upon during the Roman and Early Christian eras. Constructed on a high, artificial podium in the late third or early second century BCE, the sanctuary's core comprised a large, colonnaded courtyard, within which stood two identical prostyle temples with altars, dedicated to Aphrodite Pandemos and Aphrodite Pontia. The strategic placement of the sanctuary, facing the harbor entrance, underscores its significance for maritime activities on Kos. Following its destruction by an earthquake in 469 CE, the site entered a phase of repurposing, with building materials from the original sanctuary being integrated into a new basilica constructed during the fifth and sixth centuries. The current archaeological state thus reflects a complex history of construction, destruction, and reuse, revealing the successive cultural layers that define the ancient city's port district.

circa 180 BCE

Temple of the Attalids
The temple of the Ättalids, aligned North-South, is dated to the first half of the second century BCE and was in use until the Roman Empire period, when large-scale remodelling was carried out in this part of the ancient agora. From the Hellenistic temple only the foundation of the stepped podium is preserved, built of ignimbrite, rock, along with sporadic parts from its facade of hard grey limestone. Although no architectural parts have been found, it is reconstructed by scholars as a distyle in-antis temple of Ionic order or a tetrastyre prostyle temple of Doric order.

Around the temple, stone-built pedestals are preserved, meant probably for votive offerings, while in its vicinity part of a colossal statue was found, depicting a thorakophoros (male figure wearing a cuirass) with his himation wrapped around his waist. Carved in relief on the strut of the statue are two shields of Gallic type. The thorakophoros is identified with king Eumenes II of Pergamon (197-158 BCE), who was honoured by the Koans On the occasion of his first victory against the Gauls in 183 BCE, The organized cult of Eumenes in Kos, also known from epigraphic evidence, is attributed to the particularly close relations the two states established in that period. It is thought that a statue of the victorious king had been erected in the pronaos (anteroom) of the temple and that he was worshipped as synnaos (temple-sharing) with another deity, probably Dionysos, founder of the House of the Attalids.

circa 150 BCE

Altar of Dionysus
The Altar of Dionysus is a Hellenistic archaeological site situated in Kos Town, Greece, near the ancient Agora. The structure, constructed during the 2nd century BCE, was dedicated to Dionysus, the god of wine, ritual madness, and fertility. Excavated by the Italian Archaeological Mission in the early 1930s, the altar is characterized by its Π-shaped plan and was built from white and grey marble.

Archaeological findings indicate that the altar's exterior was once adorned with a significant relief frieze. This frieze depicted scenes from Dionysian mythology, including an Amazonomachy and a thiasus, a procession of Dionysus's followers such as satyrs, sileni, and maenads. After an earthquake in 142 CE, the altar sustained considerable damage. In the 15th century CE, the Knights of Saint John incorporated sections of the frieze into the masonry of their fortress, Neratzia Castle, to fortify the structure. Today, fragments of the ornate frieze have been salvaged and are displayed within the castle's museum.

The visible remains at the site include the rectangular foundation (crepidoma), part of the main entrance, and a stone wall. An adjacent Doric temple, possibly also dedicated to Dionysus, is part of the archaeological complex. The site is positioned approximately three meters below the level of the modern city, illustrating the historical layering of Kos town. It serves as a key testament to the island's Hellenistic-era prosperity and religious practices.

circa 1436-1514 CE

Neratzia Castle of Knights Hospitaller
Neratzia Castle in Kos Town is a striking archaeological and historical structure, built by the Knights Hospitaller between the 14th and early 16th centuries. Its construction occurred in phases, with the inner enclosure predating the outer, which was heavily fortified with massive bastions and artillery ports after 1495 to counter advanced gunpowder weaponry. The castle's most distinguishing archaeological feature is its extensive reuse of building materials, including columns, inscriptions, and architectural fragments from ancient Kos, particularly the Asklepieion. This practice is evident throughout the structure, where Hellenistic friezes with sculpted masks and garlands are integrated into medieval walls. Located strategically on a former islet at the harbor entrance, Nerantzia Castle controlled the sea passage and served as a barracks, residence for the Ottoman commander, and later a German prison. Despite suffering damage from an 1816 gunpowder explosion, the castle's restored form, shaped by Italian archaeological efforts in the early 20th century, remains a tangible record of the island's successive historical occupations.

circa 1322-1346 BCE

Antimachia Castle
Antimachia Castle on Kos is a significant example of medieval military architecture, reflecting its construction by the Knights Hospitaller of Saint John. Its history is marked by strategic relevance, serving as a prison for wayward knights and a central refuge for local populations during sieges. The castle's layout demonstrates a keen sense of defensive strategy, utilizing a hilltop location for panoramic views and a design that incorporates the natural terrain. While much of the original settlement within the walls was lost, archaeological investigation has revealed multiple construction phases dating from the 14th to the 16th century, along with additions during the subsequent Ottoman occupation. Key structural remnants include the impressive defensive walls, a massive crescent-shaped bastion at the entrance from the early 16th century, and cisterns for water supply. Additionally, two notable churches—the 16th-century Byzantine Agios Nikolaos and the 18th-century chapel of Agia Paraskevi—have survived, indicating the site's continued use long after its initial military purpose faded.