Lava Beds National Monument in northern California is home to more than 700 underground caves, but some are more exclusive than others. The monument’s magnificent Crystal Ice Cave is adorned with stalagmites and stalactites of glassy ice that extend up from the floor or hang like thick curtains from the ceiling. Because of the sensitive nature of these formations, tours are limited to just a few dozen visitors each year.
Every Saturday from January to March, the cave becomes accessible to one lucky tour group of six spelunkers. Tours can be booked three weeks in advance by calling the visitor center the morning reservations become available. Even then, the chances of snagging a ticket are slim. Candidates must be able-bodied enough squeeze through tight holes, ascend a 50-foot slope, and navigate across icy ground. They also ask that spelunkers bring all their own caving gear—provided it hasn’t been used east of the Rockies, because then it could be carrying a fungus that’s deadly to bats.
If that sounds like more trouble than it’s worth, Lava Beds is also home to the unique Fern Cave. Tours are just as restricted and only given from June through September, but this cave is much more accessible and hospitable to life. The lush, green biome is made possible by an 8-by-10-foot hole in the roof which allows fresh air and sunlight to flow in. It was also home to members of the native Modoc tribe from 1872 to ’73 during their war with the U.S. Army. They used the lava caves as their stronghold, and mortars, pestles, and precious rock art can still be found in the Fern Cave from their time there. These artifacts, along with the cave's delicate ecosystem, make it one of the most exclusive tickets out there for cave-loving adventurers.
[h/t: Indefinitely Wild]