The Trevi Fountain is the end point of the Aqua Virgo, a Roman aqueduct finished by Agrippa in 19 BC that still carries water into Rome.

• ✓Wikipedia, "Aqua Virgo"
• ✓Wikipedia, "Trevi Fountain"
• ✓Turismo Roma (official Rome tourism), Aqua Virgo Park
• ✓Encyclopaedia Romana (University of Chicago), Aqua Virgo
• ✓Frontinus, De aquaeductu (the legend of the girl and the spring)

The Trevi Fountain isn't just decoration. It's the end of a pipe. Look at the panel above the statues: a girl showing Roman soldiers a spring. That spring, about twenty kilometres away, is where this water starts. Roman engineers ran it almost entirely underground, with a fall of only about four metres over the whole distance, so gravity alone could carry the water into Rome. Goths cut it during a siege in 537. Popes repaired it again and again. Nine metres under the streets nearby, you can still see its water flowing through a Roman tank. Today it's the oldest Roman aqueduct still running. The fountain you see is only from 1762. But every coin tossed in here lands in water still fed by a tunnel Romans dug two thousand years ago. Subscribe for a fact every day.