The Great Barrier Reef (GBR) is one of the most remarkable natural wonders of the world, which is why it’s such a catastrophe that climate change-induced ocean warming and acidification is systematically destroying it. Fortunately, after 30 years of mysterious signals and unconfirmed data points, a team of researchers have revealed that there is, in fact, another.

Specifically, just behind the GBR, a much deeper reef spanning an area of more than 6,000 square kilometers (2,316 square miles) has been found. That's bigger than 7.5 New York Cities.

It is covered in donut-shaped mounds, each one measuring up to 300 meters (984 feet) across and 30 meters (98 feet) thick. These are comprised of organized growths of Halimeda, a commonplace green algae made from living, calcified sediments.

“We’ve known about these geological structures in the northern Great Barrier Reef since the 1970s and 80s, but never before has the true nature of their shape, size and vast scale been revealed,” study co-author Robin Beaman, a research fellow at James Cook University and expert in the GBR, said in a statement. “The deeper seafloor behind the familiar coral reefs amazed us.”

The new deep reef was thought to be fairly sizable, but this hidden cache is roughly three times the size of previous estimates. It stretches from just north of Port Douglas to the entire length of the Torres Strait.

Writing in the journal Coral Reefs, the team note that it was found using LiDAR, a surveying technology that uses lasers, instead of radio waves, to search for objects much in the way traditional radar does. In this case, it was deployed by aircraft from the Royal Australian Navy.