In the 12th century a tower of the Gandolfi family, lord of Castel Gandolfo, existed in the site. In 1183 Pope Lucius III gave it to the Cistercian monks of St. Anastasius of "Aquae Salviae" in Rome. In 1235 they built a large castle around which the town later grew. In 1378 the Popes assigned it to Giordano Orsini. The Cistercians and the Colonna alternatively ruled Genzano until 1563, when the castle was ceded for 150,000 scudos to the Massimi, from which it was bought by Giuliano Cesarini.