That's because there was a cave the size of mid-town Manhattan hidden beneath the New Mexican desert.
Images: Ringworld cliffs, in a space with definite boundaries, cut a world's diorama.
Through the Earth and Beyond
Someone is watching with him, through a pair of cross-time eyes that strangely resemble those of his grandfather, James Hive-Maker, as Hive-Maker will appear at a singular moment in the (at that time) future life of Zoltan Abbassid.
At the end of this vision, Jacob finds himself walking again in a dark world, heading inexorably towards someplace that he cannot name, a planet with a waiting victim.