 The Romans constructed numerous aqueducts. A surviving treatise by Frontinus, who served as curator aquarum (water commissioner) under Nerva, reflects the administrative importance placed on ensuring the water supply. Masonry channels carried water from distant springs and reservoirs along a precise gradient, using gravity alone. After the water passed through the aqueduct, it was collected in tanks and fed through pipes to public fountains, baths, toilets, or industrial sites. The main aqueducts in the city of Rome were the Aqua Claudia and the Aqua Marcia. The complex system built to supply Constantinople had its most distant supply drawn from over 120 km away along a sinuous route of more than 336 km. Roman aqueducts were built to remarkably fine tolerance, and to a technological standard that was not to be equalled until modern times. The Romans also made use of aqueducts in their extensive mining operations across the empire, at sites such as Las Medulas and Dolaucothi in South Wales.
