Related by context. Frequent words. (Click for all words.) 44 Lascaux 42 grottoes 41 caves 40 archaeological ruins 40 limestone caves 39 cave 39 lava tubes 39 limestone formations 39 Forgotten Dreams 38 Tut tomb 38 stalagmites 37 limestone cave 37 grottos 37 sarcophagi 37 sandstone cliffs 37 volcanic crater 37 stalactites 36 Giorgio Vasari 36 dinosaur footprints 36 ancient pyramids 36 underwater caves 36 Cave 36 Article PubMed ISI ChemPort 36 alpine lakes 36 stupas 35 stalactite 35 Otzi 35 Egyptian pyramids 35 royal tombs 35 Kartchner Caverns 35 mine shafts 35 seamounts 34 Caves 34 Machu Picchu 34 pictographs 34 ancient tombs 34 Lake Vostok 34 caverns 34 Apennine mountains 34 archaeologists 33 stalagmite 33 archaeological finds 33 cave explorers 33 craggy mountains 33 marine reptiles 33 melting glacier 33 Utah Crandall Canyon 33 frescos 33 cliff dwellings 33 catacomb 33 Cheops 33 Carlsbad Caverns 32 mudflat 32 harshest interrogation 32 archeologists 32 fossilized bones 32 painstakingly restored 32 limestone quarry 32 cenotes 32 rock outcrops 32 extinct volcano 32 Pritzker Prize winning 32 hibernating bats 32 medieval castles 32 archaeological sites 31 cavern 31 underground cavern 31 Judean Desert 31 middens 31 trilobites 31 cavers 31 Oetzi 31 waterfalls 31 terracotta army 31 painstaking 31 Luc Montagnier 31 lava tube 31 dinosaur fossil 31 observatory 31 Caverns 31 spelunkers 30 petroglyph 30 hot springs 30 precipices 30 prehistoric 30 hydrothermal vents 30 Tioga Pass 30 volcano crater 30 rocky outcrops 30 megaliths 30 Antikythera Mechanism 30 underground caverns 30 Seracini 30 landforms 30 mountain ranges 30 crevasses 30 entombed 30 carvings 29 Crandall Canyon 29 dinosaur fossils 29 towering cliffs