Last week we mentioned that Crystal Cave at Sequoia National Park was reopening to the public for the first time since 2021. Now we're going to tell you where else in the National Park System you can go underground.

Have you seen Yellowstone’s iconic Old Faithful Inn without its portico? Did you know employees at the North Rim’s Grand Canyon Lodge serenaded departing guests?

Uh-oh, this doesn’t look good. A kayaker is careening down the narrow winding river, letting the current pull her towards danger instead of paddling like mad away from it. “Stay hard right,” shouts Hailey Albers. “Stay away from that root wad.” Whooping and hollering, the woman rather gleefully crashes right into a partially submerged tangle of tree roots.

To be honest, I have no clue what I’m looking at beyond the fact that it’s a key object in the World War II-era race to develop the world’s first atomic weapons before Nazi Germany. There is a giant wall full of holes that reminds me of a Lite-Brite toy, mannequin men with rods and a legend that talks about donut, iodine and uranium fuel slugs.