It's a large area of old Lava flows, Lava tubes (tunnels) a beautiful quiet park. Well worth it.
This park shows many volcanic features (spatter cones, craters, lava flows, lava tube caves) that are so young that they look as if they formed yesterday.
Amazing scenery, especially if you're willing to hike. Sconchin Butte is an amazing 360° view from the firewatch tower. Highly recommend it, but it's a 500' rise in 0.7 mile distance work several switchbacks. Worth the effort though! Several historic points to see, especially related to the Modoc War. Caves are reasonably accessible. Be sure to check in at the visitor's center. They have some, but bring your own good flashlight and i highly recommend a decent helmet. Scraping your head on the cave ceiling will result in you getting to see your own blood 😉.
And petroglyphs
Old lava flow, that has cut out tunnels and caves
They are old lava flows that the outside hardened while the inside kept flowing leaving lava tubes.
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