Zion National Park, Utah. A backpacker is silhouetted against the Navajo Sandstone walls of the Virgin River in the Zion narrows of Zion National Park in southwestern Utah. The 16-mile trek through this 3000-foot deep and narrow gorge is one of the most unique walks in the world. Towering sandstone walls line the river and in places are only 25 feet wide. Escape is difficult in the event of a flash flood and many people have perished here over the years as a wall of water swept down on them as they negotiated these narrows. The waters of the Virgin River begin 8000-feet high on the Markagunt Plateau. 150 river miles later, they flow into the waters of Nevada’s Lake Mead.