The Catacombs of San Domitilla are among Rome's most atmospheric early Christian burial sites. Their underground corridors preserve tombs, frescoes, and a reconstructed subterranean basilica, giving a stronger sense of the ancient cemetery than many better-known catacombs.
They sit south of the historic centre, so combine them with the Appian Way or nearby Roman sights rather than treating them as a quick stop between central museums.