Santo Stefano Rotondo is one of Rome's strangest early churches, a fifth-century circular basilica dedicated to St Stephen. Its round plan, ring of columns, and quiet position on the Caelian Hill make it feel very different from the city's grander Baroque churches.
The church is also known for its graphic fresco cycle of martyrdoms, which can be startling even by Roman standards. Pair it with the Colosseum area or the Baths of Caracalla, both within walking distance.