“Tropical rainforest” might conjure images of close-packed trees, dense humidity, and the din of animal calls. But rainforests host landscapes beyond that archetypal one, including vast, treeless clearings that seemingly appear out of nowhere.

These strange, sudden canopy gaps, called bais, are located only in the rainforests of the Congo Basin of west-central Africa. Some stretching the length of 40 football fields, and some only a few hundred feet across, bais are the world’s largest known natural forest clearings, and they seem to play a big role in the rainforest’s highly complex, biodiverse environment.