Siena, Italy
The Tuscan city of Siena is probably best known for its Duomo and the Piazza del Campo where the Palio di Siena, a traditional medieval horse race, takes place every summer. The Duomo was originally meant to be the largest cathedral in the world, but like many grand schemes, the money ran out after the transept and the east wall were built. You can still see part of the building plan and climb the east wall. The Piazza del Campo, aka the town square, is usually bursting with tourists sitting in the middle of the square as the sun passes over the tower, waiters serving cappuccino to haggard parents, and kids chasing a few pigeons by the fountain. Siena deserves more than a day trip, but if that is all you have you will certainly catch the highlights.