洞穴

洞穴	dòng xué	cave / cavern
洞	dòng	cave / hole / zero (unambiguous spoken form when spelling out numbers) / CL:个
洞	tóng	used in 洪洞 (the name of a place in Shanxi)
穴	xué	cave / cavity / hole / acupuncture point / Taiwan pr. [xue4]