Aqueduct of Segovia.
It is probably the best and more complete aqueduct remaining from those built at Roman Empire age, not only because of its good state of preservation, but only for its design, dimensions and concept.
It has suffered several partial restores, rebuildings and, even, partial elimination of ashlars, specially cornices.
Greatness, harmony and integration given by this work to the city did provoke that restoring works did keep original design. The most outstanding between them was made by Catholic Kings. Aqueduct is doubtless the most artistic and monumental ingeneering work from Roman History.
Datation could be difficult since there are neither clear documents nor inscriptions to establish origin of building. It has been thought to be built by Traian, Claudius, Nerva or a Domitianus. Anyway can be assured that it was built at the end of 1st century or beginning of 2nd one..
This aqueduct takes water from Frio river at 18 km. from the city, the Roman Secovia. It is driven through a canal 0,30 m. wide and 0,30 m. deep. It goes on an open course until pine-wood of Balsaín. There, it becomes underground up to a first sand filter -turris aquae-. Then, current runs on a wall -a part of the conduction today lost- that ends at a second filter deposit. This one is protected by a rectangular box. Its plan is 7,70 m. x 4,80 m. with a barrel vault slightly pointed. Inner pool has a plan of 4,30 m. x 2,20 m. and 2,60 deep. It was composed by six files of ashlars.
From this second deposit cames out an elevated conduction known at the whole world. It is composed by 166 semicircular archs -68 single and 44 doubles superimposed-. The whole is 638 m. long.