In front of the Bolsena Castle (Rocca Monaldeschi) is the Palazzo Monaldeschi. It is the museum seat, detached from the Territorial Museum of Bolsena Lake.
The Palazzo Monaldeschi exhibits artefacts from various historical periods: Etruscan and late Etruscan finds from Civita d'Arlena and Roman finds from Volsinii. Besides it hosts medieval and renaissance ceramics, found in the "butto" of the main tower of the Rocca and other ceramics of various origins.
Particular interest is given to the exhibition of wrecks and objects lost and found in the lake, including the remains of an American B-17 bomber that crashed into the lake during World War II in January 1944.