Niter Ice Cave, Ice cave in Grace, Idaho.

Niter Ice Cave is an ice cave that forms as a long winding lava tube about 1,200 feet (365 meters) deep, with ceiling heights varying between 15 and 25 feet (4.5 to 7.5 meters). The floor remains icy and wet throughout the year, with water seeping from above and creating layered ice formations on the walls and ground.

A volcanic eruption thousands of years ago likely formed the lava tube that became Niter Ice Cave. Early settlers near Grace, Idaho, stored food and collected ice there year-round, and the site later served as a picnic and recreation spot.

The cave's walls carry drawings and graffiti left by generations of visitors, from early settlers to recent hikers. The name "Niter" refers to the nitrate-rich earth found in the cave, which early settlers collected for use in making gunpowder.

The cave lies about 3 miles south of Grace, Idaho, in open farmland. Bring a flashlight and warm clothing, as the interior stays cold year-round, and wear sturdy shoes because the floor is icy and wet from water seeping through the ceiling. Watch your footing on the uneven lava-tube floor.

The cave is a lava tube formed by a volcanic eruption thousands of years ago, roughly 3 miles south of Grace. Early settlers stored food and collected ice here year-round, and drawings and graffiti remain on and around the ice.