The Narrows is the most popular hike in Zion National Park, and one of the world's best slot canyon hikes. It is pure fun and can be tailored to suite any ability level. The trail is basically the Virgin River. The canyon is so narrow, the river covers the bottom in many spots, which means you have to wade or swim to proceed. Plan on being wet. In fact, the cool water makes this hike particularly pleasant during the hot months of summer.