Ancient volcanic activity formed the 650-foot-long, four-section Gular Ice Cave lava tube, which during pioneer times supplied ice for the towns of The Dalles [1] and Hood River. Accessible from Ice Caves Campground, six miles west of Trout Lake [2], the cave entrance is a collapsed sink, 15 feet across and 14 feet deep, connected to three other collapsed sinks by passageways.
Wear warm clothing and sturdy boots, and bring at least two dependable flashlights. A helmet is also a good idea. The cave is managed by the Forest Service.
Links:
[1] http://www.moon.com/destinations/washington/columbia-gorge-and-wine-country/the-columbia-gorge/the-dalles
[2] http://www.moon.com/destinations/washington/south-cascades/mount-adams/trout-lake-and-glenwood