Oceanographers aboard the EV Nautilus vessel discovered what appeared to be a brick road at the bottom of the ocean in late April.

The team of researchers were exploring the ocean floor around the Papahānaumokuākea Marine National Monument, an underwater volcanic mountain range off the coast of Hawaii, when they happened to find the road-like structure, according to the New York Post. The discovery was livestreamed on the Luʻuaeaahikiikekumu expedition’s YouTube channel.

“Are you kidding me? This is crazy!” one researcher exclaimed as the team came across the structure almost 3,400 feet under the ocean surface. Less than 3% of the 583,000 square miles of the Papahānaumokuākea has been recorded, despite the peaks summiting more than 16,000 feet, rising to around 200 feet below the surface, the NY Post noted.