Boyd Cave: Staircase into the Sagebrush
Bend, Oregon
Boyd Cave is a well-preserved lava tube, roughly a third of a mile long. What makes it unusual is its location -- the middle of a flat, otherwise empty field of Oregon sagebrush -- and its entrance, which is a metal staircase descending into the earth. What's also unusual is that the staircase and cave are open to the public, free, any day of the year, any time of day.
The cave is unlit, except for light coming through the entrance hole, and is a chilly 42 degrees year-round. Because it's a lava tube, Boyd Cave's crusty interior is particularly dark, so bring a backup flashlight in case your first one goes out. Also, it's a wild cave, so don't expect any flat or manmade surfaces. Except for the stairs.