The Catacombs of Domitilla, which are situated on the ancient via Ardeatina, are the best-preserved and the most extensive (17 kilometres) in Rome. Their origin dates back to some burial grounds that were built on a property belonging to Flavia Domitilla, a noblewoman and the niece of Flavio Clemente, who was a consul in 95 CE.
In addition to the galleries on four different levels, the Catacombs of Domitilla comprise a semi-underground basilica, which was built during the pontificate of Pope Siricius (r. 385-99). The basilica is dedicated to St Nereus and St Achilleus, two soldiers who were probably martyred during the reign of the emperor Diocletian (r. 284-305).
A cubiculum contains a fresco that is the earliest known depiction of Christ as the Good Shepherd. The catacombs, the only ones still to contain bones, were in use from the 2nd until the 9th century. They were then abandoned until their rediscovery a thousand years later.