I get the impression that very few people bother to visit the remains of Ancient Ostia’s synagogue. These are located some 300 metres outside the Porta Marina, the gate that faced the sea in Antiquity. The location feels rather isolated, and the situation was probably not very different some 2.000 years ago: Jews were often seen as marginal in the Greco-Roman world. The Jews themselves ignored the gentile world around them and gentiles ridiculed the Jews for their Sabbath, food taboos and male circumcision.
Relations between the Romans and the Jews go back to the second century BCE. We know that a Jewish diplomatic delegation arrived in Rome in 160 BCE. The envoys made a treaty of friendship between the Roman Republic and the Maccabees (later: Hasmoneans) of Judea, and perhaps some of them stayed in Rome as ambassadors. The treaty – which was renewed twice in the 140s – may also have encouraged migration to Italy. Relations seem to have been cordial, and in 142 BCE, the Maccabees received a friendly letter from a Roman consul. And yet three years later the Jews seem to have been expelled from Rome by the praetor peregrinus.
The incident is badly documented, but apparently the Romans felt that some activities of the Jewish community constituted religious proselytism and this was seen as a threat to the Roman state religion and Roman public morals. The Jews were certainly not gone for good. In the first century BCE Rome had a thriving Jewish community again. Jews settled in other cities in Italy as well (in Aquileia for instance). There were good reasons for Jews living in the Diaspora to travel to Ostia and settle there, as it was a major commercial centre with contacts all over the Mediterranean world.
The first synagogue of Ancient Ostia was built in the mid-first century CE, but the remains of the building that we see today mostly date to the fourth century. The synagogue was located directly on the Via Severiana, the road that ran along the coast from Ostia to Tarracina (also known as Anxur). It was also close to the ancient beach, and therefore close to the sea. Although not much is left of the building, it is still possible to reconstruct the layout of the ancient synagogue. This was by no means a large building. There was a vestibule with a low basin which has been identified as a mikveh, i.e. a bath used for ritual purification. Behind that was the central cult room. Still standing is the propylaeum, the ornamental gateway which in this case is made up of four columns. We can also still see the remains of a semi-circular aedicule in which the Torah scrolls were kept.
The room to the south of the vestibule was used as a kitchen, as is evidenced by the presence of an oven and a counter. To the west of the kitchen was a large room which may have been the dining room or perhaps an assembly room. It had benches along the walls. Some evidence that this site was a holy place for Jews has been preserved in situ: one of the mosaics shows a Solomon’s knot. The symbol is certainly not exclusively Jewish, but for the Jews it seems to have represented eternity. Unfortunately the synagogue of Ostia did not last forever: use of the building was discontinued in the fifth century.
 Cambridge Dictionary of Classical Civilization, Paperback edition 2008, p. 474.