Once out of the oaks he found again the low terrace of aspens, and above that the wide, open terrace fringed by silver spruces.
This side of the valley contained the wind or water worn caves.

As he pressed on, keeping to the upper terrace, cave after cave opened out of the cliff; now a large one, now a small one.

Then yawned, quite suddenly and wonderfully above him, the great cavern of the cliff-dwellers.
It was still a goodly distance, and he tried to imagine, if it appeared so huge from where he stood, what it would be when he got there.

He climbed the terrace and then faced a long, gradual ascent of weathered rock and dust, which made climbing too difficult for attention to anything else.

At length he entered a zone of shade, and looked up.
He stood just within the hollow of a cavern so immense that he had no conception of its real dimensions.