On the drive from Yellowstone to Crater Lake, before you hit the onion country of eastern Oregon, is a little visited National Monument and Preserve called Craters of the Moon. It’s almost as startling as driving up on the Grand Canyon, you’re just cruising through Idaho and all of a sudden you’re surrounded by lava flows. The campground alone is cool, it’s built into the lava rocks so each campsite is secluded and the road blends in with the black rocks. We did not go into any caves (I think they were actually closed because of COVID) but there are many to visit.
There’s a ton of park to explore, but with just a day there we ended up doing the North Crater Trail out to the spatter cones and back (3.5 miles round trip). You can also get to the Snow Cone on a scenic drive if you don’t feel like walking but the trail crosses some lava flows, weaves through some amazing trees growing in the lava, and loops along massive craters.
(Check out the full map at the NPS website)
Even though Idaho is pretty far north I’m glad we were there in October, with all of that black rock absorbing the heat and nothing between you and the beating sun I can imagine that summer in Craters of the Moon is absolutely baking.