Largest Roman aqueduct (still in operation)
Segovia aqueduct
20.3 mile(s)
Spain (Segovia)

The largest Roman aqueduct still in use (after an amazing 19 centuries) is at modern-day Segovia in Spain. Probably first constructed in the first century under the emperors Domitian, Nerva and Trajan, it transports water over 20.3 miles, from the Fuenta Fría river to Segovia. The impressive engineering includes numerous settlement tanks, cleansing basins, channels and bends. At its tallest, the famous 683-m-long bridge section reaches 28 m high above two rows of 166 single and double semi-circular arches supported on 120 pillars. Nearly every pillar and spandrel has a different design.

The "opus quadratum" granite blocks of the bridge section are laid without mortar – probably due to a lack of local limestone to make cement – making the aqueduct flexible enough to survive small earthquakes, settling and wind buffeting. Around 7,500 m³ of granite, weighing 20,000 tons, were used. The largest block weighs 2 tons.