40 Horse Cave is a fun, family-friendly cave tucked into the rocky walls of Wolverine Canyon, on public BLM land about 15 miles from Firth, Idaho. It's reached by a scenic drive up well-maintained Wolverine Road, with a parking area a couple of miles into the canyon, and there are no fees. The cave gets its colorful name from a pair of local legends — one tells of two men caught in a storm who ducked inside, one remarking that “this cave could hold about 40 horses”; another claims a thief once stashed 40 stolen horses here to avoid capture. Either way, the roomy opening makes the tall tale easy to believe.

The hike up to the cave is short but steep — only about 500 feet long with roughly 100 feet of climbing, yet it earns every step. There are two ways up: the shorter, more direct route is a loose shale scramble that's genuinely slippery (hikers and kids alike tend to slide around, even in good boots), while the slightly longer trail is still steep but holds much less shale and makes for a far easier descent. A common strategy is to grind up the short shale route and come down the gentler one.

Inside, the cave runs only about 25 to 50 feet deep, so a flashlight isn't strictly required — but a few nooks and back corners are more fun to poke around with a light, and kids can easily spend half an hour or more exploring. Keep an eye out for the rock chucks (yellow-bellied marmots) that sun themselves on the boulders around the canyon.

There's more to discover nearby. At the bottom of the trail, a culvert near the road becomes a fun place to splash around when the creek is running high. And if you follow the faint trail in the willows on the southeast side of the road for about 100 feet of easy walking, you'll find a smaller second cave worth a look.

Wolverine Canyon itself is worth the trip. Its rugged rock walls draw rock climbers, the creek and cottonwoods make for pleasant camping and picnicking, and the quiet canyon is good for wildlife watching — deer, raptors, and those ever-present marmots. Many families make a half-day of it, combining the cave with a creekside lunch and a wander among the canyon's formations.

A few practical notes: Wolverine Road is usually in good shape, but it can occasionally be closed to vehicle traffic, so it's worth checking conditions before a long drive. The canyon is a shared landscape of public land and working ranches, so respect any private property and livestock you encounter, leave gates as you find them, and pack out your trash. Bring water, sturdy shoes with good grip for the shale, and sun protection, and enjoy one of eastern Idaho's most enjoyable little cave adventures.

Seventeen Mile Cave is an easy, family-friendly lava tube out on the volcanic plain about 17 miles from Idaho Falls, Idaho — the source of its name. Formed by the flowing lava of the Snake River Plain's volcanic past, the tube was left hollow when the molten rock drained away, leaving a tunnel you can walk right into. Its easy access and gentle floor make it one of the most popular beginner caves in eastern Idaho, drawing spelunkers from Idaho Falls and Rexburg alike.

The entrance sits just a few hundred feet from the highway, and the cave runs a little less than a quarter mile back. What sets Seventeen Mile Cave apart from most lava tubes is its floor: instead of the usual jumble of collapsed rock, much of it is smooth and nearly flat, which makes walking the length of the cave surprisingly easy. There's one main tunnel that's simple to follow — no real chance of getting lost — making it a great first caving trip for kids and newcomers.

At the far end, the quarter-mile passage finishes at a pair of small pools and a swampy area; it's difficult to push much beyond this point, so most explorers turn around here. Along the way, the cave stays cool and humid year-round no matter how hot the desert above, so it's a refreshing escape on a summer day — and a genuinely chilly one in the shoulder seasons.

Come prepared with the caving basics: bring at least two light sources per person (the cave is completely unlit), wear a jacket or extra layer for the cool interior, and put on sturdy, closed-toe shoes, since the floor is damp and can be slick near the pools. It's a short trip, but a headlamp that frees your hands makes it far more enjoyable.

The cave is one of many volcanic features scattered across this stretch of the Snake River Plain, a landscape built by ancient eruptions and riddled with tubes, cracks, and cinder cones. That makes it a natural first stop for local families and Scout groups getting into caving, and an easy add-on to a day of exploring the wider volcanic country around Idaho Falls. Bring a group — caves are always more fun, and safer, with company — and let someone know where you're headed.

One honest note: because it's so close to town and so easy to reach, Seventeen Mile Cave gets heavy traffic, and it shows — the walls carry a lot of graffiti and the floor collects litter. Do the cave a favor by packing out everything you bring (and maybe a bit extra), skipping the spray paint, and treating the place with respect, so this accessible little lava tube stays a fun introduction to caving for the next family that comes to explore.