A storm knocked electricity out, preventing lifts from bringing nightshift workers to the surface.

Photographer Tamara Merino and her boyfriend were driving through the desert in Australia in November 2015 when they started to see a few odd signs: “Underground bar,” then “underground restaurant.” After they got a flat tire, they found an underground church — empty, but lit by a few flickering candles. They had stumbled into the city of Coober Pedy, a partly subterranean community and the opal capital of the world. The town’s name comes from the Aboriginal phrase “kupa piti,” or, roughly, “white man’s hole.”

After Russian mining company Alrosa recently dug up a huge 76.07 carat diamond, we look at the most expensive in the world.