A group of prospectors crossing through the inhospitable terrain of Southwestern Nevada in the 19th century discovered a cavern they named the Devil’s Hole, an opening to an underground aquifer that houses a population of small fish known as Devils Hole pupfish. These fish are some of the rarest in the world: Four times a year, federal and state scientists in scuba gear count the fish, which have evolved to survive in the pool’s extreme conditions.

A mile from Devils Hole, a replica of the cavern has been constructed from concrete and fiberglass, its contours an exact copy of the original. Even the algae and invertebrates that inhabit the real pool have been recreated. Finished in 2013, when the wild population hit a low point, the facility now houses about 50 fish. The facsimile is a response to the problems facing the real version. In the 1960s, a developer used the aquifer to grow alfalfa, which caused the water levels to drop, endangering the pupfish. In the 1970s, the federal government sued the developer and the draining stopped, but water levels never fully recovered, so federal agencies have had to supplement the cavern’s food, making the wild fish and those in the fake tank highly dependent on people for survival.