sinkhole

noun 0.591

cavern

noun 0.574

cenotaph

noun 0.567

cave

noun 0.558

blue hole

noun 0.553

teocalli

noun 0.553

cistern

noun 0.547

canyon

noun 0.545

grotto

noun 0.533

cist

noun 0.519

palenque

noun 0.518

cove

noun 0.510

speleothem

noun 0.502

aquifer

noun 0.502

cisterna

noun 0.501