Lava Beds National Monument lies on the broad northern flank of Medicine Lake Volcano, a low-lying shield volcano that last erupted about 1,000 years ago. Its most distinctive feature is a vast network of more than 300 lava tube caves, several of which penetrate as far as 150ft below the earth's surface; others extend horizontally for thousands of feet. The rugged terrain was also the scene, in 1873, of a brief but bloody war between displaced Modoc Indians and US Army forces.Begin at the visitor center, where rangers and interactive displays interpret the lava beds' natural and human history. The center offers maps, books and hardhats for purchase; visitors may borrow flashlights at no charge for exploring the caves. The Mushpot Cave (entrance near visitor center) is a good place to begin exploring the park's many lava tubes. It was named for the unique formation created when a burst of lava penetrated its floor from a channel just below. The 2mi Cave Loop Road circles around an area of hardened lava that flowed from Mammoth Crater, located just inside the monument's southern boundary. Winding beneath the lava carapace is the park's densest concentration of lava tubes, many of which are indicated and accessible by parking areas and improved stairways. Visitors can explore any or all of the caves to see various types of lava and lava formations and to sample the eerie, chilly darkness of these mysterious underground spaces.