First discovered in the 17th century by the Maltese scholar Antonio Boso, the subterranean Jewish catacombs on the outskirts of Rome are some of the oldest monuments to the European Diaspora. Additional Jewish burial sites, not to mention many Christian ones, were also unearthed in the 19th century. Saul Jay Singer outlines their history:
Ancient Roman law prohibited burial within the city, so catacombs were established in the soft volcanic rock outside the city walls. These Roman catacombs, which feature about a half-million tombs interred in a complex underground network of narrow passageways and dark galleries, contain the largest body of archaeological evidence on the early Christian and Jewish communities of ancient Rome.
Intriguingly, [modern] radiocarbon dating suggests that Jewish catacombs may have preceded Christian catacombs and that their use may have actually been of Jewish origin, as Jewish immigrants from the Middle East brought their traditional burial practices to Rome and influenced the Romans to abandon their customary cremation funerary practices. Indeed, according to Leonard Rutgers, an archaeologist for Utrecht University and an expert in Roman Jewish catacombs, radiocarbon analysis by atomic-mass spectroscopy shows that Jewish catacombs predate their Christian counterparts by at least a century.
An unsolved mystery, however, is where Jews—who are known to have been living in Rome at least as early as the 1st century BCE—buried their dead before the initial construction of the Jewish catacombs around the late-1st to 3rd centuries CE.