The aqueduct once transported water from the
Rio Frio, situated in the mountains from the city in the
La Acebeda region. It runs before arriving in the city. The construction of the aqueduct follows the principles laid out by
Vitruvius in his
De Architectura published in the mid-first century BC. The water was first gathered in a tank known as
El Caserón (or
Big House), and was then led through a channel to a second tower known as the
Casa de Aguas (or
Waterhouse). There it was naturally
decanted for
sand to settle out, and the water continued its route. Next the water traveled on a one-percent
grade until it was high upon the
Postigo, a rocky outcropping on which sits the walled city center with its
Alcázar or castle. To reach the old city, the water is conveyed by its aqueduct bridge. At
Plaza de Díaz Sanz the structure makes an abrupt turn and heads toward
Plaza Azoguejo. It is there the monument begins to display its full splendor. At its tallest, the aqueduct reaches a height of , including nearly of
foundation. There are both single and double
arches supported by
pillars. From the point the aqueduct enters the city until it reaches Plaza de Díaz Sanz, it includes 75 single arches and 44 double arches (or 88 arches when counted individually), followed by four single arches, totalling 167 arches in all. The first section of the aqueduct contains 36 semi-circular arches, rebuilt in the 15th century to restore a portion destroyed by the
Moors in 1072. The line of arches is organized in two levels, decorated simply, in which simple moulds hold the frame and provide support to the structure. On the upper level, the arches are 5.1 metres (16.1 ft) wide. Built in two levels, the top pillars are both shorter and narrower than those on the lower level. The top of the structure contains the channel through which water travels, through a U-shaped hollow measuring 0.55 tall by 0.46 metre diameter. The top of each pillar has a cross-section measuring 1.8 by 2.5 metres (5.9 by 8.2 feet), while the base cross-section measures 2.4 by 3 metres (7.9 by 9.8 feet). The aqueduct is built of
unmortared, brick-like
granite blocks. During the Roman era, each of the three tallest arches displayed a sign in
bronze letters, indicating the name of its builder along with the date of construction. Today, two
niches are still visible, one on each side of the aqueduct. One of them is known to have held the image of
Hercules, who, according to legend, was founder of the city. That niche now contains an image of the Virgin. The other one used to hold an image of Saint Stephen, now lost.
Distribution of the water Within the walled city there was a distribution system via a deposit called a
castellum aquae. While the details of this system are not fully known, it has been established that the water followed a subterranean route. The main channel has been marked on the city's pavements. == Subsequent ==