The oldest of the catacombs is hands-down the overall winner for most enjoyable experience underground. Groups are relatively small, and guides are entertaining and personable. The catacombs—Rome’s longest at 18km (11 miles)—were built below land donated by Domitilla, a noblewoman of the Flavian dynasty who was exiled from Rome for practicing Christianity. They were rediscovered in 1593, after a church abandoned in the 9th century collapsed: The visit begins in this sunken church founded in a.d. 380, the year Christianity became Rome’s state religion.
There are fewer “sights” than in the other catacombs, but this is the only funerary burial site where you’ll still see bones; the rest have emptied their tombs to rebury the remains in ossuaries on the inaccessible lower levels. Elsewhere in the tunnels, 4th-century frescoes depict some of the earliest representations of Saints Peter and Paul. Notice the absence of crosses: It was only later that Christians replaced the traditional fish symbol with the cross. During this period, Christ’s crucifixion was a source of shame to the community. He had been killed like a common criminal.