Look down at the Colorado River nearly directly below the Echo Cliffs you can see a large boulder in the middle of the river. The boulder is reportedly the largest boulder lying in the Colorado River for the entire stretch of the stream all the way to Lake Mead. The large rock has fallen into the river at a location where the right and left banks are already close together. The rock splits the stream of the river into two narrow channels. Because of the narrow banks and narrow channels, this location is called Boulder Narrows.