The Aqua Marcia was the longest of Rome’s aqueducts, running nearly 60 miles from its source in the countryside to the heart of the city. It was built between 144 and 140 B.C. by Julius Caesar ...

They built them there because the land dips down before rising again to the hills in Rome. If they had to build an aqueduct only five feet high, they would build a wall. But above that ...