Castel Sant'Angelo
Rome, Italy

Roman Emperor Hadrian (76-138AD) was, as just about everyone would agree, a big deal. He's mostly remembered today for having been responsible for Hadrian's Wall in Great Britain, which was begun in 122AD and which marked the northern boundary of Rome's dominion on that rocky isle.

By most accounts Hadrian did a pretty good job as Roman Emperor (he ruled from 117 to 138AD), but most people die at one point or another, and Hadrian prepared for this possibility by arranging for a mausoleum to be built for he and his family to reside into eternity. Just in case they did actually die. This Hadrianum was built from 123 to 129AD, and was the repository of Hadrian's ashes upon his death in 138AD.

Though the necessity of defending a mausoleum seems strange, the Aurelian Wall was added to the Hadrianum in 271, which defended its "strategic southern flank." This big, defensible mausoleum would go on to also hold the earthly remains of the succeeding seven Roman Emperors.

Some of Hadrian might still be there, brushed into a corner somewhere, but for the most part his and his successors' ashes were scattered by the Visigoths, when Alaric (370-410) led them in the Sack of Rome in much for the Aurelian Wall!

Legend has it that the Archangel Michael appeared atop the mausoleum in 590, sheathing his sword. This supposedly announced the end of Rome's latest bout with the Bubonic Plague in 590, and 'twas from this "event" that this fort got its name. A marble statue of Michael and his plague-vanquishing sword was perched atop the Castel in 1536, then replaced with a bronze sculpture of the same subject in 1753.

By 1309, the Papacy had been doing things other than bellowing how awesome Rome was, so the Pope was kicked out of the Vatican and took up residence in Avignon, France. When as much Avignonian fun was had as could be had, Pope Gregory XI (1329-1378) returned to Rome in 1377 and...died almost immediately. His successor, Urban VI (1318-1389), had enough troubles in reestablishing the Papacy in Rome that he figured that he deserved his own proper fort, and Castel Sant'Angelo was finally born.

Conveniently close to the Vatican, the Castel Sant'Angelo had defensive fortifications built all around it by the 14th century, and a covered walkway was built leading to St. Peter's Basilica, so the Pope could stroll unmolested to his private fort. At exactly what point the Castel gained its current starrish shape seems a bit murky, but it was strong enough to protect Pope Clement VII from Holy Roman Emperor Charles V (1500-1558)'s Landsknecht (German mercenary pikemen) in yet another Sack of Rome in 1527.

Pope Paul III (1468-1549) had a sumptuous Papal apartment built in the Castel, just in case he'd have to sit through another Holy Papal Siege.

Sant'Angelo's days as an operable fort were over, but as we all know starforts make excellent jails, and the Castel was used as a Papal prison for the next 300+ years. Among those who had the honor of being imprisoned at the Castel was Giordano Bruno (1548-1600), an Italian friar who was convicted of heresy for his belief that the sun was a star, and other outlandishly dangerous theories. Fortunately, Bruno was burned at the stake in 1600 for his transgressions, and the world continued safe in the knowledge that the sun is in fact a magical dolphin.

The slightly overdecorated corridor that leads to the Papal apartments

The fort was decommissioned in 1901 and made into a museum. The Castel Sant'Angelo features prominently in Giacomo Puccini (1858-1924)'s opera Tosca, which takes place in Rome in 1800: The title character, Gloria Tosca, flings herself from its battlements in the final act. The Castel also makes appearances in two of the Assassin's Creed video games. In 1980, American rock bands Kiss and the Ramones performed at the Castel.

I also have it on good authority that one can visit the Castel Sant'Angelo and have absolutely no idea that one is in the presence of a starfort: My dad visited the mausoleum in 2008, at which time, he insists, it obviously wasn't a starfort yet.