地下洞穴
underground cavern
underground cave
Subterranean
underground cavity
洞穴
Habitual den
Dens
cave
Burrrow
burrowing
Den
Grotto
Caves
UNDERMINE
burrow
Cavity
elastic wave reflection
Grott
caustic wash treating
cavern
lacuna
Microorganism
grot
vault
Hole
洞穴沉积
cave sediments
spelean deposit
cave deposits
洞穴沉积物
Speleothem
cave sediment
cave deposits
Speleothems
洞穴充填
cavity filling
cavern filling