The beginnings of Segovia are also not definitively known. The Vaccaei people are known to have populated the area before it was conquered by the Romans. Roman troops sent to control the area stayed behind to settle there. The area fell within the jurisdiction of the Roman provincial court (Latin conventus iuridici, Spanish convento jurídico) located in Clunia.

The aqueduct once transported water from the Rio Frio river, situated in mountains 17 km (11 mi) from the city in the La Acebedaregion. It runs 15 km (9.3 mi) before arriving in the city. 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 meters (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 meter diameter. The top of each pillar has a cross-section measuring 1.8 by 2.5 meters (5.9 by 8.2 feet), while the base cross-section measures 2.4 by 3 meters (7.9 by 9.8 feet).

The aqueduct is the city's most important architectural landmark. It had been kept functioning throughout the centuries and preserved in excellent condition. It provided water to Segovia until the mid 19th century. Because of differential decay of stone blocks, water leakage from the upper viaduct, and pollution that caused the granite ashlar masonry to deteriorate and crack, the site was listed in the 2006 World Monuments Watch by the World Monuments Fund(WMF). Contrary to popular belief, vibrations caused by traffic that used to pass under the arches did not affect the aqueduct due to its great mass. WMF Spain brought together the Ministry of Culture, the regional government of Castilla y León, and other local institutions to collaborate in implementing the project, and provided assistance through the global financial services company American Express.