Porto Ercole's Rocca Aldobrandesca was originally built for the Abbazia Delle Tre Fontane. The Aldobrandeschi didn't get their hands on it until the 13th century. They expanded it from humble castle into imposing fort and renamed it while they were at it!
When Porto Ercole fell into Sienese hands, the fortress was restored and refined into the beautiful building you see today. In 1487, the military engineer Francesco di Giorgio Martini made the fort even stronger and even more impenetrable, adding a moat around the walls and a chapel in the courtyard.
In the second half of the 16th century, the whole area became part of the Spanish Stato dei Presidi and the fortress was again strengthened by outer fortress bastions, watchtowers and underground tunnels that connected it to the Palazzo del Governatore.
The fortress was privately sold after WWII. The new owners transformed it into residential apartments. American writer Robert Penn Warren lived in the fortress from 1954-56 and supposedly wrote the poem that won him a Pulitzer Prize here.
Today the fortress is shaped like an uneven star surrounded by a thick stone wall. You can still see the four bastions in each corner of the castle, one of which was transformed into a lighthouse in 1862.
The main entrance is still preceded by a wooden drawbridge and in the interior courtyard are a series of buildings, a powder house, first-aid centre, two watchtowers and the old chapel.
The fortress is not normally open to visitors, but can be opened open request, so visit the tourist information centre in Piazza Roma.