In a city famous for its fountains, this one stands apart from the others because it lacks the ambition and grandeur of the others. Instead of great crashing torrents, the water flows out at a leisurely gurgle. No one is sure exactly what the fountain is supposed to honor. It is the form of a half-sunken ship with the water flowing out of it. Some see it as the ship of the Church eternally afloat in spite of impossible odds. Others think this marks the place where the Roman emperor Domitian built his great water stadium where sea battles were held. Another theory postulates that the fountain serves as a reminder that this part of Rome was often flooded by the Tiber River. Pope Urban VIII commissioned the fountain, and reopened an ancient aqueduct in the 17th century, providing water to this otherwise parched area. That has spawned a fourth theory about the fountain -- that its gentle form was simply a necessity in a part of the city with such low water pressure.