cave
From LSJ
ἔνδον σκάπτε, ἔνδον ἡ πηγὴ τοῦ ἀγαθοῦ καὶ ἀεὶ ἀναβλύειν δυναμένη, ἐὰν ἀεὶ σκάπτῃς → Dig within. Within is the wellspring of Good; and it is always ready to bubble up, if you just dig | Look within. Within is the fountain of the good, and it will ever bubble up, if thou wilt ever dig.
P. σπήλαιον, τό (Plato), Ar. and V. ἄντρον, τό, αὔλιον, τό, V. θαλάμαι, αἱ, P. and V. σῆραγξ, ἡ (Soph., Fragment; Plato, Phaedo, 110A); see den.