The Sentinel is a prominent Navajo Sandstone summit in Zion National Park, rising more than 7,100 feet near the Court of the Patriarchs and about 3,000 feet above Zion Canyon, the Virgin River, and the park road. Part of the Towers of the Virgin and a defining feature of the canyon skyline, it has also shaped the valley through dramatic geologic change. About 4,800 years ago, a massive rock avalanche called the Sentinel Slide broke from the mountain, dammed the Virgin River, and formed Sentinel Lake, whose later sediment helped create Zion’s notably flat valley floor. A landslide at its base again dammed the river in 1995.