The crystal clear volcanic lake is a wonderful spot for swimming, sailing, canoeing or just relaxing by the water. Since its main function is supplying Rome with drinking water, the pollution is limited to minimum (e.g. the motorboats are strictly forbidden).
It is located about an hour of driving time away from Rome, so if you are visiting the Eternal City and wish to relax a bit from its busy streets crowded with tourists, this is a great place to head. The best way to get there is by car because buses from Rome are rather infrequent.
There are also several little towns scattered by the lake with many picturesque old buildings which will charm you with their calm atmosphere.
Wikipedia https://en.wikipedia.org/wiki/Lake_Bracciano
Address 00061, Italy
Coordinates 42°7'18.166" N 12°13'55.699" E