Streets, including the Decumanus Maximus and Via Ostiensis, structured the city’s layout, linking key commercial, residential, and civic areas. Water infrastructure comprised aqueducts, nymphaea, fountains, and drainage systems, supplying both practical and decorative functions. Public fountains such as the Lamp Fountain and monumental water displays like the Nymphaeum of the Erotes served as sources of clean water, while underground channels managed groundwater levels and wastewater disposal. These elements collectively highlight the city’s advanced engineering and urban planning, reflecting its significance within the Roman Empire.

The infrastructure of Ostia Antica was a highly developed system that supported the city's role as a vital commercial and maritime hub. Its streets, paved with large basalt slabs, followed a structured grid, with the Decumanus Maximus forming the central thoroughfare. The Via Ostiensis, the main road connecting Ostia to Rome, was integral for trade and transport. Water supply was ensured through the Aqueduct of Tiberius, which channeled water from sources beyond the city, supplemented by wells and cisterns. Monumental fountains, including the Nymphaeum on the Plaza of Victoria, served both practical and decorative purposes, emphasizing the Roman priority of integrating aesthetics with function. Groundwater management systems were strategically implemented to prevent flooding and ensure steady water distribution. The presence of public fountains, nymphaea, and water storage facilities highlights the sophisticated urban planning that allowed Ostia to thrive as Rome’s gateway to the Mediterranean. The surviving remains of this infrastructure offer insight into the technological advancements and administrative organization that sustained one of the most important cities of the Roman world.

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Via Ostiensis
The Via Ostiensis (via Ostiense), literally meaning the "road of Ostia", was an important road in ancient Rome. It ran west 30 kilometres (19 miles) from the city of Rome to its important sea port of Ostia Antica, from which it took its name. The road began near the Forum Boarium, ran between the Aventine Hill and the Tiber River along its left (eastern) bank, and left the city's Servian Walls through the Porta Trigemina.

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Decumanus Maximus
The decumanus maximus was the city's main street along with cardo, which crossed each other at the Forum. The decumanus was the stretch of the Via Ostiensis inside the city, running east-west and turning slightly towards the south in the direction of the sea.

The porticos of the "sloping roofs" (sides of the road, some 90 meters in length) on both sides of the road, these porticos were the rain cover for small shops situated along the decumanus maximus of Ostia. There were also "rental flats" on the second story of the buildings.

The southern stretch of the cardo followed the course of the more ancient Via Laurentina inside the city; the northern stretch, built from scratch, reached the banks of the Tiber river. Otherstreets also ran towards the river, like Via della foce and the Semita (or path) dei Cippi, important for commercial purposed. Many of the Ostia's major streets were built over more ancient routes, thus explaining the irregular orientation of the various districts. There was also a dense network of smaller lanes.

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Nymphaeum on the Plaza of Victoria
The Nymphaeum on the Plaza of Victoria (Ninfeo su Piazzale della Vittoria) is located just inside the Porta Romana (Roman Gate), south of the decumanus.

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Ground Water Management and Aqueduct of Tiberius
Until the first century CE, Ostia's water supply was guaranteed by rainwater, collected in cisterns, and by wells drawing on the ground water. The city's aqueduct was built under Tiberius (circa 37-41 CE). It ended at the reservoir adjacent to the walls south of the Porta Romana. From here the water was distributed throught the city by an extensive network of cisterns and lead pipes (fistulae), inscribed with the name of the colony or of the concessionaries. The water network supplied public and private buildings; however, ground water continued to be used, with water being drawn up using wooden water wheels (noriae). The aqueduct remained in use until the fifth century CE; after its abandonment, water was once again provided by wells, some of which were dug into the middle of the streets, by now also partially in disuse.

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Nymphaeum of the Erotes
The Erotes Nymphaeum (Ninfeo degli Eroti), was built in the fourth century CE, takes the form of a single square room, closed and completely covered in marble panels, which provided a backdrop for the jets of water that gushed from a labrum (basin) set inside a central square pool. The side walls of the nymphaeum had two rectangular niches, each with a marble statue placed inside it. These were Roman copies of a type attributed to the Greek sculptor Lysippus depicting Eros stringing his bow and arenow in the Museo Ostiense, In the back wall was a semi-circular niche, perhaps adorned with a statue of Venus.

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Lamp Fountain
The Fountain with Lamp (Fontana con Lucerna), a fine marble fountain, stood along the Decumanus in front of the long porticobuilt in the Hadrianic period (circa 117-138CE) to monumentalize the street. There was probably already a basin lined with hydraulic plaster on this spot from the Augustanperiod (late first century BCE to early first century CE); the fountain was raised in the Hadrianic period to match the new street level and lined with marble in thethird century CE. Thefountain took the form of a basin decorated with a screen and completely covered in marble, with columns that may have supported a pergola. At the centre of the basin was a little pillar whose top was shaped like and oil lamp from which water gushed forth.

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Vespasianae
The vespasianae of Ostia Antica were public latrines integrated into the city’s sanitation infrastructure, reflecting the Romans’ advanced approach to urban hygiene. These facilities, often located near baths, forums, and markets, were designed for communal use and featured stone bench seating with regularly spaced openings, beneath which a continuous flow of water carried waste into the city’s drainage and sewer systems. Some of the best-preserved examples in Ostia include those near the Forum Baths and the Theatre, showcasing their strategic placement in high-traffic areas. Fresh water channels were installed for handwashing, emphasizing the hygienic measures employed in these public spaces. The vespasianae were not private but social spaces, where users engaged in conversation, reflecting the communal nature of daily life in Ostia. Their construction and maintenance were often funded by public authorities or wealthy patrons, ensuring access to essential sanitation services across the city.