The powerful fort was commissioned by Paul III Farnese at the end of the ‘salt war’ (1540). Based on the design by Antonio da Sangallo il Giovane (1540-1543), it encompassed the houses, towers and streets of an entire district, recognisable within the complex, and the consequential razing to the ground of the family houses of the Baglioni family, of the borough of Santa Giuliana, of the church of Santa Maria dei Servi and of many other medieval buildings. The Rocca Paolina was five levels high, equipped with a fort on Colle Landone and connected through a long corridor to the Rocca Minore, the so-called “Tenaglia” (tongs).

The fortress, symbol of pontifical domain, was partly destroyed in 1848, rebuilt in 1860 by Pius IX and finally razed to the ground in the same year. All that remains are the basements, partly still awaiting excavation, of extraordinary charm and uniqueness, crossed through by the escalators, used for exhibitions and as seat for the Museum services centre and the Documentation centre for the “Rocca Paolina and the City”.