The lakes of the volcanoes
Five craters full of water less than an hour from Rome, with campsites on the shore.
Northern Lazio is made of dead volcanoes, and where the vent was there is now a lake. There are five of them, all round, all deep, and all within a day of Rome: Bolsena, Vico, Bracciano, Albano and Nemi.
For campers they are a genuine alternative to the sea. The water is clean, the sites are on the shore, there is none of the coastal crowd and the evening temperature is easier to bear. Bracciano is the best equipped and closest to the city; Bolsena is the largest and has the finest towns around it; Vico is the wildest, inside a reserve.
What there is to do
Swimming, sailing, cycling round the shore. At Bracciano there is a fifteenth-century castle open to visitors; on Bolsena the Bisentina island opens in summer; in the Castelli you go to Nemi for the strawberries and to Castel Gandolfo for the view down into the crater.
One practical note: engines are limited or banned on nearly all of them, and that is why the water is so clean. Anyone arriving with a boat should check the rules of the lake first.