The massive Roman aqueduct built in Segovia, Spain, by the Roman Emperor Trajan (AD 98-117).
One of the best-preserved works of Roman engineering, the structure was built from approximately 24,000 blocks of dark-colored Guadarrama granite without the use of mortar. The above ground portion is 2,388 feet long. And it consists of approximately 165 arches that are over 30 feet tall.