South Rim, Grand Canyon
The Watchtower at Desert View was built in 1932. It used to be an observation station and convenient rest stop for the Grand Canyon visitors. The Watchtower is a re-creation of the strange prehistoric towers found scattered over large areas of the Southwest.
You can also climb the tower. But doesn't add anything to the view over the Grand Canyon. The Canyon is so deep, that a few extra meters doesn't make any difference.
I would say that the Grand Canyon is in general a tourist trap because of the huge number of tourists here from everywhere! But everyone wants to see this place, and rightfully so! Just expect to put up with hoardes of people!
However, the real tourist trap is in Grand Canyon Village, right next to El Tovar Hotel. There are a couple gift shops, which, while nice and everything, do make a lot profit selling their stuff at very high prices.