In 21 spots the roof of the cave collapsed, forming a cavern known locally as a jameo. The caves extend for 6 km (3.7 mi) above sea level and for another 1.5 km (0.93 mi) below the sea. One jameo forms the entrance to the Cueva de los Verdes. Two kilometers of the cave system were developed for tourists in the 1960s, with the cave walls illuminated by colorful lights.