This mile-long lava tube cave was formed roughly 700,000 years ago by molten rock that erupted from a volcanic vent in nearby Hart Prairie. The top, sides and bottom of the flow cooled and solidified first, after which the insides of the lava river continued to flow emptying out the present cave.

Colossal Cave Mountain Park has cave tours, hiking & biking, trail rides, camping & picnicking, terrace Café & gift shop. The campsites are tucked among the saguaro cacti and mesquite trees in Posta Quemada canyon. These grounds consist of two large areas, El Bosquecito and La Selvilla, both have water and restrooms. Additionally there are a number of smaller areas totaling 30 individual sites. Camping is first-come, first-served. This is primitive camping. No electricity or RV hook-ups available. are located in El Bosquecito and La Selvilla.

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