Rocca Paolina, Perugia

The Rocca Paolina is Perugia's most atmospheric oddity: an entire fortress and the streets it buried, now hidden beneath the modern city and crossed by escalators. After Perugia's revolt in the Salt War, Pope Paul III ordered the fortress built in 1540-1543 to crush the city's independence, and the architect Antonio da Sangallo the Younger raised it over a whole medieval quarter belonging to the rival Baglioni family, encasing their towers, houses and streets rather than demolishing them. Largely torn down after Italian unification, what survives is the eerie subterranean level, where visitors descend by escalator into a vast covered townscape of vaulted brick passages, blind windows, doorways and the stumps of medieval houses, lit and used today for exhibitions, art installations and a permanent display on the fortress's history. The experience is free and takes only thirty to forty-five minutes, but it doubles as the most evocative way to travel between the lower car parks and the historic centre, emerging dramatically at Piazza Italia. Because it is a through-route, it is busy at commuting times and quieter in the early afternoon; the cool air makes it a welcome refuge on hot summer days. Photography is allowed and the brick vaults are strikingly atmospheric. There is no admission charge, and the escalators run from early morning until the small hours. The Rocca Paolina sits at the southern edge of Perugia's old town, the regional capital of Umbria, linking Piazza Partigiani and the minimetro to the centre, and is easily combined with the nearby Corso Vannucci and Palazzo dei Priori.