Segovia's Roman aqueduct ranks with the Pont du Gard in France as one of the greatest surviving examples of Roman engineering, and it's the city's main sight to see. If you take the AVE in from Madrid on a day trip, the inner-city bus drops you right there. Stretching from the walls of the old town to the lower slopes of the Sierra de Guadarrama, it's about 2,952 feet long and rises in two tiers—above what is now the Plaza del Azoguejo, whose name means "highest point"—to a height of 115 feet. The raised section of stonework in the center originally carried an inscription, of which only the holes for the bronze letters remain. Neither mortar nor clamps hold the massive granite blocks together, but the aqueduct has been standing since the end of the 1st century AD. Its only damage is from the demolition of 35 of its arches by the Moors—the arches were later replaced on the orders of Ferdinand and Isabella. Steps at the side of the aqueduct lead up to the walls of the old town.
Pl. del Azoguejo, Segovia, 40001, Spain