The Romans were well known for their elegant aqueducts and carefully engineered water control. The tall ribbed construction at the left side of this picture is a water tower, or castellum aquae in Latin, that collected, stored and dispersed rainwater. It was part of a complex water system installed by the Roman colonists about 80 BC. The water towers--there are about a dozen of them in Pompeii--were built of concrete and faced with brick or local stone. They stood up to six meters in height and had a lead tank at the top. Lead pipes running underneath the streets took the water to residences and fountains.
At the time of the eruptions, the waterworks was being repaired, perhaps having been damaged by earthquakes in the months before the final eruption of Mt. Vesuvius.
Sources
For more on the archaeology of Pompeii, see Pompeii: Buried in Ashes. Also see the Walking Tour of the House of the Faun.
Beard, Mary. 2008. The Fires of Vesuvius: Pompeii Lost and Found. Harvard University Press, Cambridge.
