While taking a family tour of Washington we had heard of a lesser known hiking cave; Ape Caves. To hike it you need all your own equipment and lights although it is open to the public. We went down around sunset and instantly noticed why we all needed lights. The cave/tunnel was bored out by lava millions of years ago. There are no artificial lights in the cave and a lot of it has caved in though you can still climb through the ruble.