We hiked the Subway in Zion National Park a few weeks ago. It was incredible! Nine miles of hiking, swimming, scrambling, freezing, sweating, photographing, (have I missed anything?) oh yeah- water-sliding- through fields, slick rock, and slot canyons. Highly recommended for anyone in good enough shape!
It was so fun, and our "host family," the Holdens- Natalie's in laws- were so fun to spend time with. I hope to repeat this hike in the future. And if only I could upload more than 2 or 3 photos at a time I'd post a few more. Oh well.