In Zion National Park, up the North Fork, lies the Subway. Canyoneers access it from the "top down", repelling through waterfalls and swimming through pools. Hikers & photographers access it from the "bottom up". There are no official trails, but because of the popularity, many trails braid either side of the river. There are many river crossings to get there, which, depending on the water levels, can be trivial or mid-thigh deep.