Antiquity did not merely interpret dreams of caves; it went into caves to dream. Incubation, sleeping in a sanctuary to receive a healing or prophetic dream, was organised practice in the Greek world, and the darker oracles took the descent literally: at the cave of Trophonius in Boeotia the inquirer went down into the earth by night through a narrow opening and came back with what was shown, shaken enough that proverb said those who consulted Trophonius forgot how to smile. The cave was the architecture of revelation, the place where the daylight self is set aside.
Religious history kept faith with the shape. Muhammad received the first revelation of the Quran in the cave of Hira; Elijah heard the still small voice at the cave on Horeb; the hermits of several traditions chose caves as the fit setting for vision. Plato's cave in the Republic runs the image the other way, the cave as ordinary unenlightened life, which only shows how strong the figure is, since even its reversal kept the terms.
The psychological traditions read the dream cave in the incubatory spirit: the Jungian school takes descent into the earth as entry into the unconscious, the cave as the chamber where what is buried, treasure or fear, is kept, and the return to daylight as the point of the journey. Popular dictionaries compress this to hidden depths and retreat. The readings are the traditions' own; the cave's credentials as a place of disclosure are historical fact.