The Nankoweap granaries were built by Puebloans in 1100 AD.  The tightly built structures were built to protect food from rodents and preserve corn and seeds for long periods in the dry climate.  The site is only accessible by rafting the Colorado River or descending 6000’ from the rim on the Nankoweap Trail.  From below is by far the easiest requiring only a 500’ ascent, on a steep trail, from the river up the side of a cliff.