floor, stalactite, stalagmite

cavern, mountain, canyon, tomb, crevasse, mineshaft, stalactite, gorge, waterfall, mountainside, stalagmite, spelunker, burrow, carlsbad caverns, spelunk, lair, prehistoric, crevice, icefall, archaeologists, kiva, hibernaculum, glacier, cenote, cavelike, coal mine, hut, grottoes, castle, cave dweller, dungeon, karst, hideout, ledge, wilderness, toltecs, quarry, hallstatt, coalmine, mountaintop, volcanic crater, tartarus, volcano, climbers, monastery, crag, fossils, gasherbrum, rockface, cellar, refugium, archeologists, excavations, crater, snailfish, lascaux, fumarole, dinos, hot springs, cappadocia, postholes, boulder, cliff, snowfield, mine, chomolungma, backcountry, stratovolcano, campsite, couloir, sarcophagus, yurt, cove, underground, bivvy, hogback, fumaroles, hermitage, igloo, ravine, expedition, mountaineers, ichthyosaur, lava, nanga parbat, catacombs, tunnel, ark, archeological, hiding, lizard, mount ararat, petroglyph, massif, tumulus, himalayas, tufa, iguanodon, pictograph, glacial boulder, tsangpo, timberline, grotto, caves, caverns, lake, crypt, grottos, loch, watercourse, bed, river, room, square, ruined, magdalenian, neolithic, paleolithic, palaeolithic, plundered, unexcavated, built, chalcolithic, fortress, haunted, ridden, balinese, desolated, etruscan, excavated, heathen

grot, sap

aisle, ali baba, antrozous pallidus, caveman, cavern, cave bat, cave dweller, cave man, cove, creepy-crawlies, dead sea scrolls, fingal's cave, floor, flow, grot, grotto, hydromantes shastae, lascaux, mouth, olm, pallid bat, proteus anguinus, shasta salamander, staffa, stalactite, stalagmite, stygian, tenebrous, troglodyte, undermine, wall

core out, enclosure, explore, hollow, hollow out, natural enclosure