Located at Hoover Dam, there are four intake towers in total. Two are located on the New California Republic side of the Hoover Dam checkpoint, and the other two are on the Caesar's Legion side of the checkpoint. An NCR guard stands at the door to intake tower 1. Each intake tower's interior is slightly different than one another, each one numerically labeled above the doorway.
The Hoover Dam intake towers appear only in Fallout: New Vegas.
Behind the scenes
The Hoover Dam intake towers are based on the four towers emerging from the real world Lake Mead, to the north of the Hoover Dam. Two of the towers are located on the Arizona side and two on the Nevada side.