The Horse Lava Tube System is a vast network of lava caves in central Oregon stretching from Newberry Volcano north past Bend toward Redmond and nearly to Crooked River Gorge. Formed about 80,000 years ago by the Horse Cave lobe of the Lava Top Butte basalt, it filled an ancient Deschutes River channel and now includes 122 known caves with more than 22,000 feet of traversable passage. People have used caves in the area since prehistoric Native American times, and some were known by the 1870s and early 1900s. Today fragmented ownership, urban growth, vandalism, and dumping threaten the system, prompting cleanup, mapping, and management efforts.