Craters of the Moon
Normally I'm all over things volcanic, but this national monument didn't live up to expectations.
The NPS describes it as a "vast ocean of lava flows" but the parts of it I saw weren't vast. A rangerette wouldn't give me a permit for the lava tubes trail because I couldn't account for the whereabouts of my boots. I might have worn them into another cave in the past and, to avoid White Nose syndrome you aren't supposed to track between caves. At least El Malpais National Monument has hydrogen peroxide that you can soak your boots in, but Craters didn't.