Secrets of the Underground (2017)
| First Air Date: | 2017, February 14 |
| Last Air Date: | 2017, December 16 |
| Status: | Ended |
| Seasons: | 2 |
| Episodes: | 16 |
| Episode Runtime: | 60 min |
| Countries: | United States of America |
| Production: | Science Channel |
Overview:
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.