Kalalau Trail, Na Pali Coast Wilderness Park, HI
Picture the most perfect jungle hike you can imagine and you'll envision something a lot like Kauai's Kalalau Trail. This 22-mile roundtrip journey through sultry tropical wilderness and up jagged volcanic rock that ends in a pristine remote beach can get rough (volcanic rock in particular isn't very forgiving on flesh) with perilous ridge walks and three major stream crossings. There's also the danger of falling rocks, possible flash floods during storms, and one particularly adrenaline-charged ledge crossing. In light of the strenuous conditions day-use permits are no longer issued and visitors are required to get a camping permit rather than attempt a near marathon-length journey in a single day. Oddly though, it turns out the perilous trail is less responsible for mishap than beach visits, as over 100 people have died in the rough isolated waters along the way.