How Nemi was built and evolved over time

Nemi is built on volcanic rock and around a hole in it.

The territory was shaped by the eruptive activity of the Vulcano Laziale between about 600,000 and 20,000 years ago, leaving a soil composed largely of volcanic material rich in peperino and tufo — and the historic centre itself stands on a mass of lava above the crater.

The Roman building was on the shore rather than the rim. The Temple of Diana Nemorensis was erected around 300 BC on the northern shore of the lake, beneath the cliffs where the modern town now stands.

What happened to it afterwards is a model of how ancient sites disappear: abandoned in the late imperial period, with portions of its marbles and decorations removed, then gradually covered by forest and generally left undisturbed for centuries until amateur excavation began in the 1600s.

The most remarkable engineering here was Roman and hydraulic, and it was reused nineteen centuries later: the ships were exposed in the twentieth century by lowering the lake level through underground canals that the ancient Romans had dug.

In the town, the surviving fabric is later: a few late medieval to eighteenth-century churches, and the Castello Ruspoli.