It, like most of Rome's treasures, is tucked away among a maze of winding little streets. Suddenly you burst into the sunlight, and there before you is the 1762 creation of Nicola Salvi -- although it was planned a century earlier by Bernini.

Water passes through it from an aqueduct, called the Acqua Vergine (Virgin Spring), originally built in 19 BC.

If you want to return to Rome, you must throw a coin over your left shoulder into the pool. I threw in a roll of quarters.