Aqueducts

Aqueducts (synonyms: waterworks) are large structures that carry water from a water source such as a river, lake, or spring, to a place of use such as a town or city. In worldbuilding they are often a type of megastructure that is found as ruins from an ancient civilization. When designing aqueducts consider the source of the water and where it is being brought. Typically aqueducts are pictured as constructed of stone.
Aqueducts may be especially important in desert locations.

In our own world the Romans created extensive networks of aqueducts, many of which still stand today.