Located in Lassen National Forest off Highway 89, a tenth of a mile from Highway 44, the cave is a lava tube, formed during a lava flow that covered the Hat Creek Valley some 2000 years ago. It extends about 1300 feet.
Subway Cave is a self-guided trail. Subway Cave is the largest accessible tube in the flow. Temperature inside the cave remains a cool 46 degrees year around. Be sure to take a jacket with you. The cave is open late May through October. Subway Cave is closed during the winter months. Visibility in the cave is zero. Take a dependable flashlight with you. There are self-guided trail signs inside. Admission to the cave is free.