Bandera Volcano and The Ice Cave.
The Bandera Crater erupted around 10,000 years ago and after the eruption, the lava suddenly fell back down the main vent making the bottom of the cone deeper than the outside lava flow. The crater that remains is nearly 1200 feet wide at the top and roughly 750 feet deep.
The Ice Cave is located in part of a 17 mile long collapsed lava tube where the temperature never rises above 31 F. The natural layers of perpetual ice glisten blue-green in the reflected rays of sunlight. They say that the floor of the ice is approximately 20 feet thick and that the deepest ice dates back to 1100 BC