The Romanesque church was converted from a nymph of the villa of Emperor Domitian built in the first century AD. The building has a square base and is topped by a dome. Inside the plant is circular with four large semicircular recesses corresponding to the corners of the outer perimeter. The floor still has sections of the original mosaics and inside there are marble remains and important frescoes of the thirteenth and fourteenth centuries of the Roman school of Cavallini. The church has a magnificent thirteenth-century bell tower.