official website: http://www.archeologia.beniculturali.it/pages/atlante/S173.html
This is the largest and the most complete Roman villa in northern Italy, situated at the outmost point of the Sirmione peninsula on Lake Garda. Actually it was probably not a property of Catullus, but of a family belonging to the Valeria gens, and the poet might have been their guest for a time, which would have given origin to the legend.
The villa was built soon after the Augustan period (1st century AD) on a rectangular plan 167m long and 105 wide, covering about 20,000 square meters. It consisted of 3 floors, with the main entrance to the south, where also the spas were located. On the long sides there were covered porches, joined to the north in a panoramic terrace overlooking the lake. At the center was a wide open space, covered today with olive trees. Below the villa are previous constructions of the 1st century BC, and it is historically certain that it was already abandoned in the 5th century AD. The name grotto came to be used after the fall of the Roman empire, when many ceilings collapsed and the site was filled with vegetation.
In the Antiquarium, situated to the right of the entrance, there are items found in the villa as well as other specimens from the Neolithic to the Middle Ages found in the Sirmione peninsula, fragments of frescos, mosaic paving, ceramics and coins. The antiquarium, beautifully organized with panels and charts of the place as it must have been in its days of splendour, also collects frescoes of the late 1st century AD with sea scenes, and a mysterious portrait of a poet, which many like to believe to be a representation of Catullus himself.
The seminal research on the site was by archeologist Girolamo Orti Manara of Verona in the late 19th century. Then the Soprintendenza Archeologica della Lombardia (a branch of the Italian Ministry of Culture and Arts) purchased the whole site in 1948. Studies and excavations are still being made.