According to some historians, it was erected on the foundations of an earlier construction in 1489. The clock on the façade is composed of two dials (one facing Piazza del Plebiscito, the other towards Via Roma) which were produced in the ceramic factories of Civita Castellana, replacing those removed in 1983 (which are currently being restored).

Each consists of 100 polychrome majolica tiles. One dial was made by Francesco Ercoli of Viterbo in 1816 and the other by the Richard Ginori factory in Florence at the end of the 19th century.