Fortezza Pia, 16th-century fortress in Ascoli Piceno, Italy

Fortezza Pia is a fortress built in the 16th century on Annunziata Hill overlooking Ascoli Piceno. It features angled bastions and thick reinforced walls that form a classic Renaissance fortification structure.

The hill held a fortress since Picene-Sabine times; Gnaeus Pompeius Strabo destroyed it and Rome rebuilt it. Ascoli's commune reconstructed the citadel between 1185 and 1195, Frederick II demolished it a third time, and Galeotto Malatesta restored it in 1349. Pius IV had it rebuilt from 1560, and the French dismantled it in 1799.

The name comes from Pope Pius IV, who had the fortress rebuilt from its foundations in 1560; a stone portal on the east side bears the inscription "Pius IV medic. Medio/Pont. Max/Moenia e fundamentis/Erexit MDLXIV". The ashlar portal and the eastern bastions are the elements to look for today.

The surviving walls face north and the bastions stand on the east side, where a squat portal of dressed stone bears the inscription recording Pius IV's work of 1560-1564. The site is on the Colle dell'Annunziata, the highest part of Ascoli Piceno, and is half-hidden by vegetation, so the remains are reached on foot along the hill.

Hidden passages run beneath the fortress, linking it to other defensive structures in town through an underground network. This tunnel system within double walls allowed defenders to move secretly between positions without being seen.