1.   In the field opposite are fissures in the underlying limestone, entrances to long subterranean passages.

2.   Scientists believe that these exotic life forms travel in watery subterranean passages that connect Yellowstone to mid-ocean ridges and other extreme, hot environments.

3.   Visitors would enter through subterranean passages and emerge at a memorial to Newton built at the base.

4.   But just outside, the curious can still be found at any hour, peering down into the subterranean passage.