How Sutri was built and evolved over time

What distinguishes Sutri is that its principal monuments were excavated rather than constructed.

The Roman amphitheatre was completely excavated out of the tufa. Instead of raising tiers of masonry, the builders removed rock until an arena remained — an approach that only works in a soft volcanic stone and produces a structure that cannot collapse in the ordinary way, because it is a void rather than a pile.

The Etruscan necropolis uses the same logic at a smaller scale: dozens of tombs, likewise cut into the tufa.

The Mithraeum was cut into the rock as well, and then converted — transformed into a church dedicated to the Madonna del Parto, so the excavation changed religion rather than being replaced.

Above, the walls record two phases at once: Etruscan masonry incorporated into the medieval circuit, so the defences were extended rather than rebuilt.

And the Duomo, of Romanesque origin, is the conventionally built element in a town whose other monuments are hollowed out of a single imposing tufa relief above the Via Cassia.