Gardner Cave
Gardner Cave is located in extreme northeastern Washington state inside Crawford State Park. Gardner Cave is the longest limestone cave in Washington state with a length of 1,055 feet (322 m). Only the first 494 feet (151 m) are open to public access. The cave is adorned with stalactites, stalagmites, flowstone, pools, and a column 2 feet in diameter.
Cave data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).