Aqua Virgo is one of the 13 aqueducts built to deliver water to the city of Rome. Built by Agrippa in 19 BC its source was an area eight miles to the north of the city. Almost all of the Aqua Virgo ran underground. The water is unsuitable for drinking but it is still the source of water for the Trevi Fountain and other fountains on the Campus Martius.
The aqueduct at Frejus in southern France was built in the first century AD, taking water 26 miles from the source at Neïssoun to the coastal town of Frejus. Over 22 miles of the channel are hidden from view with only 1 mile carried on bridges. The aqueduct was brought back into use in 1874 to irrigate the surrounding land. Since then, it has been further repaired or renewed to once more bring fresh water to Frejus.
The Proserpina Dam that fed the aqueduct taking water to the nearby town of Merida is still used by local farmers to irrigate crops. Its dimensions are breathtaking given its age: 466 yards wide; 23 yards high and 2-1/2 yards wide at the top. Thick buttresses on both the inside and outside of the dam add stability when the water is drained.
The Aqueduct of Segovia is worthy of special note for its almost uninterrupted use from its construction to the present day. It is also notable for the magnificent bridge running 746 yards across 75 single arches, then 44 double arches over two tiers. The viaduct is a maximum of 31 yards high and is built from over 20,000 granite blocks. The bridge and the old town of Segovia is now recognized as a UNESCO World Heritage site.