The magnificent natural scenery of the Lake Nemi with its characteristic form of volcanic crater, hides a treasure trove of priceless historical value still largely unknown. A trail along the shore of the lake leads to the entrance of the famous Emissary, a 1,600 m long tunnel dug into the rock in the fifth century. BC, which flows into the nearby valley of Ariccia. The culvert regulated the water level of the lake, which was thus also used for irrigating the fertile valley Aricina. Entirely feasible if equipped with flashlights and hard hats, the emissary appears as a true manual of the ancient hydraulic engineering so praised by Pliny and Vitruvius.
On the banks of the lake rises the Ship Museum where you can admire the remains of the famous Roman Ships, real floating palaces decorated with bronzes and marbles, which were built under the Emperor Caligula and later sunk at his death. They were recovered at the bottom of the lake after his partial drying up in the ’30s.
A little higher up, overlooking the lake can still be seen the ruins of the Sanctuary and the Temple of Diana Nemorense, one of the most ancient of the Lazio, whose history is linked to one of the most bloody sacrificial rites of antiquity.