Hell's Half Acre, Idaho

An interpretive nature trail takes visitors though an incredible 5,200 year-old basaltic lava flow with paved walkways. Twenty-five engraved signs on the hike identify aspects of the lava flow's unique ecosystem. While it has been designated a wilderness study area, the wilderness designation has never been made. The best time of the year to visit is May or September. More at VisitIdaho.com