洞 - den, cave, excavation

hollow; cavity; hole; cave

cave; cavern; den; grotto

discernment; insight

cavity; hollow; cave; cavern

cave; cavern; grotto

limestone cave; limestone cavern

G8 Hokkaido Toyako Summit; Hokkaido Toyako G8 summit

cavity resonator; microwave resonance cavity; rhumbatron

making hollow; making meaningless

vaginal cavity; vagina

Soto school (of Zen Buddhism)

geode