San Leo's fortress sits on a sheer block of rock above the Montefeltro hills, a natural stronghold long before Federico da Montefeltro had it rebuilt in 1441 by his military architect, Francesco di Giorgio Martini.
The new walls followed the cliff edge so closely that an attacker had nowhere to plant a ladder, and for centuries the Papal States used the fortress as one of their most secure prisons. Its best known inmate was Giuseppe Balsamo, the self-styled Count Cagliostro, an alchemist and occultist held in a cell reachable only through a trapdoor in the ceiling, where he died in 1795. Today the rooms hold a museum of arms and armor, and the ramparts give a clear view over San Leo's rooftops and the winding road below. The short, steep walk up from the village is worth it for the view alone, quite apart from the history.
