Photograph of a view of the portal to one of the four, 56-foot diversion tunnels for the Hoover Dam, [s.d.]. At center, a large cavern is cut into bedrock, supported by circular scaffolding. At left, wooden framework supports a conveyor belt.; Caption reads: "View of portal of one of the four 56-foot diversion tunnels. These tunnels, each approximately 4,000 feet in length are being lined with three-feet of concrete and will be used to divert the waters of the Colorado River during the construction of Hoover Dam." Photoprint reads: "Los Angeles Aqueduct construction, [s.d.]."