Fontana di Treve, or Trevi Fountain as we Americans call it, is thought to get its name from the three streets (tre vie) that come together at this rather small piazza. Although the present fountain wasn't finished until 1732-1751, it was started some hundred years earlier. Its source is still the Aqua Vergine aqueduct, although for the past 40 or so years it has been chemically treated and partially recirculated by a system of electric pumps. The fountain was cleaned and restored for the first time from 1989-91, but needed it again by 1999. The large archway represents the palace of Neptune. Neptune is in the statue in the chariot drawn by sea horses. Other white marble statues also adorn the beautiful fountain.
We took the metro to the Spagna station, checked out the Spanish Steps, then walked the couple blocks to the little intersection where the Trevi Fountain is. It's not a really large fountain and it's in a built-up part of the city, but it's still a pretty sight. There are plenty of signs around the central part of the city to steer you in the right direction.
This fountain was rarely visited before the movie Three Coins in a Fountain was made. Now it's Rome's most visited fountain. It's a beautiful spot to stop and rest for a while on the abundant concrete bench seating facing the fountain. There's even a drinking fountain there for refilling your water bottle. But it's not recommended that you drink from the Trevi fountain because of all the chemicals in it. And, yes, we threw a couple coins in the fountain to make sure that we'll be going back.