In June 2011, I visited the historic city of Segovia, Spain. One of it premier tourist attractions is its ancient Roman aqueduct.
According to an article titled “Saving Segovia’s Aqueduct” written by Norma Barbacci (ICON Magazine, Winter 2006/2007):
Begun in the second half of the first century AD, the aqueduct at Segovia is a materpiece of Roman engineering, which continued to provide the Spanish city with potable water well into the 20th century. The aqueduct system stretches some 15 kilometers, from its origins at a freshwater source in the Sierra de Guadarrama southwest of the city to the Alcazar, a medieval castle built atop Roman remains on a precipice. . . . Together with the walls of Tarragona, the aqueduct is one of the two largest surviving Roman structures in Spain.
For most of its route, the aqueduct traverses the landscape through a series of ducts and underground channels. Only for its final stretch, where the system must bridge a deep depression at the Plaza del Azoguejo just below the old part of town, however, does it reach a full height of nearly 30 meters. There, where many of the main roads into Segovia meet, 118 pillars continue to suppor a two-storey arcade.
Thought to have been commissioned by the Flavian emperor Domitian (81-96 AD), the aqueduct was first repaired at the request of Trajan in 98 AD, according to the remains of an inscription that graces one of the lower arches. Although the gilded bronze letters of the inscription have long since vanished, holes form the lead pegs that once held them have permitted the text to be read. Fourteen of the surviving pillars were completely rebuilt between the fourteenth and nineteenth centuries.
Despite its high profile and Segovia’s inscription on UNESCO’s World Heritage list in 1985, the aqueduct had, until recently, been threatened by lack of Maintenance, differential decay of its individual stone blocks, water leakage from the upper viaduct, and in some ares pollution, which has caused the granite ashlar masonry to deteriorate and crack. In an attempt to address the conservation problems the Junta de Castilla y Leon, the regional government launched a campaign to preserve the aqueduct in 1992, an effort underwritten in large part by Caja Madrid, one of Spain’s leading banks.
One of the aqueduct’s most interesting features is its second sand trap. Before reaching the Segovia, the water was treated to remove impurities. There are two undercover tanks for this purpose. The second of the two, known as a “water tower,” regulated the flow as well as the quality.