It is home to a palace which was owned by the Farnese family; it was commissioned by Pope Paul III to (allegedly) Antonio da Sangallo the Younger on the site of the medieval castle.

Of the castle, only few traces remains, including a defensive tower, the entrance arch and few parts of the walls; its ditch has been now transformed into roads and squares.

Gradoli borders the following Comuni: Bolsena, Capodimonte, Grotte di Castro, Latera, Montefiascone, Onano, San Lorenzo Nuovo, Valentano.

Gradoli's origins date to the Middle Ages, when a castle was built here: this could be reached only through a series of steps (in Latin, gradus), whence its name.

In 1978, during the kidnapping of Aldo Moro, Gradoli was mentioned (in an alleged séance participated by future prime minister Romano Prodi) as the possible location of the politician and therefore searched.