This mausoleum was probably built around 30-20 BC. Therefore it is at a very low level. It has a rectangular base of travertine and tufa (6.80 x 6.80 m.). The base supported a cylindrical upper part (diam. 5.11 m.), lined with marble, largely disappeared. The base has a rectangular exedra at the front, flanked by two semicircular exedrae with small benches. In the central exedra are also benches, supported by dolphins. Amongst fragments of marble, located to the north of the tomb, are two blocks of Carrara marble, one decorated with the prow (rostrum) of a war ship, the other with three swords and a lion's head.

In view of the rostrum the deceased must have had a connection with a naval war. It cannot have been Caius Cartilius Poplicola, who was buried in a mausoleum on the other side of the street (IV,IX,2). According to Bouke Van der Meer it will have been Publius Lucilius Gamala, who gave Ostia money for a bellum navale, probably the war against Sextus Pompeius Magnus in 38-36 BC. The adjacent House of the Thunderbolt (III,VII,3-4) may have been used for funerary meals.