Green Lake - Carlsbad Caverns National Park, New Mexico - Scenic Green Underground Chamber

The Green Lake Room is one of many highly decorated scenic chambers within the complex of 84 major caves at Carlsbad Caverns National Park. Unlike the many rooms noted for their stalagmites and stalactites, the specific highlight of this chamber is a green-hued pool of water located in a corner of its uppermost floor.

It was first believed that the green color of this "lake'' was caused by microbes or an algae-like film beneath its surface. However, later investigation showed that the color of Green Lake comes from a carbonate mineral lining its sides and bottom: Malachite. Also known as "copper carbonate,'' the green-colored mineral crystallizes to form stalagmitic masses. As light shines through the water, it reflects the malachite's deep green color.

In the late 1940s, the U.S. military undertook a series of tests at Green Lake to evaluate its feasibility for use as an emergency fallout shelter. During an atomic test at a distant facility, no ripples were observed on the surface of the water here, leading officials to believe the Green Lake Room would be a safe haven in the event of nuclear attack.

Green Lake is featured on two tour routes at Carlsbad Caverns. The self-guided tour starting at the Natural Entrance leads 1?-mile past the Green Lake Overlook, while the mile-long King's Palace Guided Tour takes a paved trail right through the chamber. The latter costs $8 and departs from the Underground Rest Area.