The round lake has very few towns on the lakeshore, namely the neighbouring towns of Marta and Capodimonte in the south end and Bolsena in the north end of the lake.
Bolsena has a fine historical profile with the churches Basilica di Santa Cristina, Chiesa del SS. Salvatore and of course medieval castle Castello Rocca Monaldeschi di Bolsena. The town is also home to many beautiful places and the historical museum of Lake Bolsena. Down by the lake shore you will find a marina and a small ferry berth from where you can take tours around the lake.
From here you can take a cruise on the lake on boats that depart from Bolsena and go out to the islands of Bisentina and Martana (the lake's only two islands). Overall, it is a beautiful area with forests and rolling hills and a really good starting point for exploring central Italy: Etruscan area, Umbria (where you can visit Orvieto's underground city) and Tuscany and the Eternal City of Rome.