Villa of Lucius Cassius Tertius, also known as the Villa B, is another significant complex in Oplontis, situated some three hundred meters to the east of the opulent Villa Poppaea. Lucius Cassius Tertius is believed to have been the last owner, as evidenced by a bronze seal bearing his name found during the excavations. Currently, the building is still being excavated and is not open to the public. Constructed towards the end of the second century BCE and later expanded, the villa is organized around a central space, encircled by a double-order colonnade made of grey tuff. This colonnade has been meticulously reconstructed using the original column drums and capitals, which have been restored to their original positions.

circa 50 BCE

In contrast to the lavishly adorned Villa Poppaea, the neighboring villa is a rustic, two-story structure with many rooms left unplastered and featuring tamped earth floors. This villa was occupied at the time of the eruption, as evidenced by the remains of 54 people found in one of its rooms, who perished in the surge that struck Oplontis. Among the victims' belongings were fine jewelry, silverware, and coins totaling 10,000 sesterces, making it the second largest monetary find in the Vesuvian region after Boscoreale.

Some rooms appear to have been used for manufacturing, while others served as storerooms, and the upper floor contained the living quarters. These details, along with the recovery of over 400 amphorae during excavations, suggest the villa was dedicated to the production of wine, oil, and agricultural goods. The discovery of various weights supports this theory, and a bronze seal bearing the name Lucius Crassius Tertius, presumably the villa's last owner, was also found at the site.

A series of structures on the lower floor were likely storehouses, as suggested by the materials found within them. The branches of the peristyle served as storage areas for transportation containers, primarily wine amphorae, many of which were stacked upside down against the walls. The discovery of a pot containing conifer resin, used to coat the inner walls of amphorae, atop a stone stove, combined with the absence of production facilities, suggests the villa functioned as a horreum for storing local farm produce and trading locally produced wine.

On the northern side of the building, there are small, independent, two-story structures overlooking a street that separates them from buildings on the opposite side. These were likely small shops with living areas on the upper floors. The complex thus appears to have been a genuine insula, delimited by streets.

On the southern side, other storehouses with vaulted ceilings were found, where 54 people tragically perished while seeking refuge from the eruption. Many of these individuals had taken their most prized possessions with them, resulting in the discovery of a significant quantity of gold and silver coins and numerous high-quality jewels. A precious wooden safe, decorated with iron and bronze, had fallen from the upper level during the collapse and contained various items of jewelry. The upper floor on the southern side seems to have been residential, possibly housing the owners, with rooms adorned with Fourth Style paintings.