One of the best preserved Roman constructions, the Roman Aqueduct at Segovia was still in use as recently as 50 years ago. Constructed around AD 50 during the reign of the Roman Emperor Trajan out of some 200,400 granite blocks, the aqueduct was made without concrete and stands due to the equal balance of forces. When in use, it carried water from the River Frio to the city of Segovia over a distance of 16km (ten miles). The portion of the aqueduct that is above ground is 728m (2388ft) in length and consists of 165 arches, each over 9m (30ft) high, which are spectacularly illuminated at night. It is possible to climb a staircase next to the aqueduct to get views over the structure itself as well as the city.