Scientists have discovered a massive ancient forest 630 feet below the surface of a sinkhole in China’s Leye-Fengshan Global Geopark.

The region is home to the world’s longest natural bridge and caves, according to UNESCO. It’s located in the Guangxi Zhuang Autonomous Region of China.

“The UNESCO Global Geopark is primarily sedimentary with more than 60% of 3000m thick Devonian to Permian carbonate rocks,” according to UNESCO’s website.

“It forms an ‘S’-shaped structure and a rhombus configuration in the karst areas of Leye and Fengshan counties respectively, which controlled two large subterranean rivers’ development, the Bailang and Poyue.”

“In addition, between these two subterranean rivers the Buliuhe River was formed. Around these rivers, it formed numerous karst geosites including high karst peak clusters (fengcong), poljes, karst springs, karst windows (tiankengs), natural bridges, extensive caves, massive cave chambers and speleothems.”