COLONIAL AQUEDUCT 
Calle Rufino Tamayo (northern extensión of García Vigil), Centro Histórico
Shortly after the founding of the city in the 1520s, a rough canal was built to supply water to the settlement from a mountain spring to the north. In the 1730s this canal was reconstructed into a graceful, green stone aqueduct that served as the main water provider to the city until 1940. The aqueduct piped water directly to wealthier Oaxacans and fed a series of public fountains, the source of water for most of the city's residents. Many of these fountains survive, although few still function. Look for a fountain at the corner of San Felipe Neri church, one on Fiallo alongside San Agustin church, another near the state artesanía shop Aripo on García Vigil, and another on M. Bravo. The remains of the aqueduct itself can be seen by walking north on García Vigil until it becomes R. Tamayo; the aqueduct runs atop an arched brick wall through a charming neighborhood of the city, appropriately called Los Arquitos, and thence through the barrio of Xochimilco. Another section lines the road to San Felipe del Agua, the source of the water.

From page 15-16 of Oaxaca Tips