From the BBC, some facinating information about the war fought underground during WW1.
'Archaeologists are beginning the most detailed ever study of a Western Front battlefield, an untouched site where 28 British tunnellers lie entombed after dying during brutal underground warfare. For WWI historians, it's the "holy grail". '
Click on the link to read the full article.
http://www.bbc.co.uk/news/magazine-13630203