 Later, the eruption of voluminous pyroclastic flows, and volcanic ash, caused the progressive collapse of the volcanic cone, which created the caldera, in which Lake Vico now lies, by about 138,000 years ago.The lake is drained by the River Vicano.Before the construction of a tunnel by the Etruscans, the lake was probably deeper than today, the Monte Venere constituting an island within it.