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Researchers diving off the coast of Tahiti, French Polynesia’s largest island, have discovered a vast reef of giant rose-shaped corals. The yet-to-be-named reef is almost two miles long and roughly 100 to 200 feet across. Lying in the “twilight zone,” between 100 to 215 feet below the surface, it’s unusually deep for a tropical coral reef, which may explain its “pristine” condition—it appears to be neither affected by climate change nor spoiled by human activities.

The reef was first discovered in November last year by divers from the seafloor exploration project Ocean 1. “It was magical to witness giant, beautiful rose corals which stretch for as far as the eye can see,” says Alexis Rosenfeld, an underwater photographer and founder of the 1 Ocean project, which is jointly run by UNESCO. “It was like a work of art.”

The 1 Ocean team has spent approximately 200 hours studying the reef, including taking photos, measurements and samples of the corals. The reef is predominantly made up of Pachyseris speciosa, a plate-like coral that forms rose-shaped colonies that can grow to be 6.5 feet wide.

Laetitia Hedouin, a coral expert at the French National Center for Scientific Research who is involved with the project, hopes the research can help experts understand the role deeper corals might play in the ocean ecosystem. “The discovery of this reef in such a pristine condition is good news,” says Hedouin, “and can inspire future conservation.” More dives are planned in the coming months.