Until 1996, two of Egypt’s greatest cities were missing. Then along came French archeologist Franck Goddio, who made an extraordinary discovery underwater.

For 1,000 years, Thonis-Heracleion was completely submerged. Fish made their homes among the rubble of mighty temples; hieroglyphs gathered algae. Gods and kings sat in stasis, powerless, their statues slowly withdrawing from the world, one inch of sand at a time. Goddio spent years surveying this find, as well as neighboring Canopus, which was rediscovered by a British RAF pilot in 1933 who noticed ruins leading into the waters.

Thanks to a new exhibition at the British Museum, Goddio’s incredible finds will soon be open to the public.

Sunken Cities: Egypt’s Lost Worlds opens May 19, and according to museum curator, Aurelia Mᴀsson-Berghoff, the exhibition pulls back the curtain on what was once one of archeology’s greatest mysteries.

“(Thonis-Heracleion and Canopus) were known from Greek mythology, Greek historians and Egyptian decrees, and now we know where they were.”