He thought of it as a hill, for he had lived long in the heart of the towering Andes.

Behind him lay the belt of woodland that separated the basin from the open sea, a scant league away.

The cleft through the hill lay almost directly ahead.

It's walls apparently were perpendicular; a hundred feet or less from the pinnacle, the opening spread out considerably, indicating landslides at some remote period, the natural sloughing off of earth and stone in the formation of this narrow, unnatural passage through the very centre of the little mountain.

For at least a thousand feet, however, the sides of the passage rose as straight as a wall.