Secrets of the Underground - Season 2 - Eps 6: Mystery of the Ice Cave
A strange cave freezes in the summer and melts in the winter, and a massive sand dune swallows a small child in an instant. Rob Nelson and Stefan Burns use cutting-edge technology to investigate these mysteries of the natural world.
About Secrets of the Underground

Title: Secrets of the Underground
First Air Date: 2017-02-14
Last Air Date: 2017-12-16
Status: Returning Series
Rating: 4.3/10 (from 3 votes)
Language: EN
Seasons: 2
Total Episodes: 16
Network: Science
Genres: Reality, Documentary
Production Companies: Science Channel
Synopsis
A search for an underground escape route said to have been used by Al Capone. Also: who or what built earthen mounds in Washington state.