Part of World War I took place in tunnels near No Man’s Land, where men and officers could plan and rest in relative safety. Now historians and archaeologists are rediscovering these tunnels-- that is, after they pump out thousands of gallons of water that has accumulated in some of them in the ninety years since WWI ended:
If you don't get the Morlock reference in this post title, rent the George Pal film The Time Machine (1960) starring Rod Taylor and (yowsa!) Yvette Mimieux. Eye-popping color, great sets, plus it's a very faithful adaptation of the classic novel by H. G. Wells.
If you would actually like to read the Wells novel (and novels by Wells, Dickens, or Kipling are excellent cold winter's evening reading), you can get it for free as an etext or audio book at Project Gutenberg.