Ignazio of Loyola

It was during those years that a bloody dispute arose between the Castellani
(inhabitants of Castel Madama) and the Tiburtini, because of taxes to be paid for the transit of goods through Tivoli. 

In 1540 the Castellans set fire to Porta San Giovanni (near the Tivoli Hospital). 

The Tiburtines, after they had avenged themselves, rebuilt the Gate on which they wrote, “Ignitas portas extinsit sanguine Tibur” meaning “Tivoli extinguished with blood the burned doors.”

Cardinal Bartolmeo della Queva tried to calm tempers, but only Ignatius’ intervention finally succeeded in restoring peace. 

The cardinal, among other things, reclaimed the area of the springs of the Acque Albule, creating an outflow channel to the Aniene River.

Rocca Pia was built by Papa Pio II (Enea Silvio Piccolomini) in 1461, straddling the city walls built by Federico I Barbarossa, fortifying and enlarging them, to control the road to Abruzzo but also to dominate the rebellious city of Tivoli. 

On the entrance portal to the fortress it says as a warning: 

“Grata bonis, invisa malis, inimica superbis sum Tibure: enim sic Pius instituit” 
and that is, “Here I am, I am here for you, O Tivoli, well liked by the good, frowned upon by the wicked, an enemy to the proud: for Pius II so willed.”