The Piazza Navona (or Navona Square) is one of Rome’s largest and most elaborate public squares, with three fountains and surrounded by a number of fascinating buildings. The square also hides a secret - it was built over the ruins of the ancient Stadium of Domitian and it’s now possible to access the remains underneath the busy square overhead. Tickets for the Piazza Navona underground include an audio guide, or if you want to stay above ground consider a guided tour of the square to learn more about its history and architecture.