That is speculation, but it is intriguing.
hey guys – here is the link to the full video: https://www.youtube.com/watch?v=yCy8iWxf1Us&feature=youtu.be&t=459 – Outer Dark
Creepy voice enhancement through Soundcloud :
YT description: A man stumbles upon something strange in a deep underground mine, which sounds just like an underground military bunker, or D.U.M.B
Title: Explorer stumbles onto ACTIVE Secret military BUNKER! #Conspiracy (YT link) Uploaded by The Outer Dark.