CRREL Permafrost Tunnel, 23 meters into the adit.
Visit http://permafrosttunnel.crrel.usace.army.mil for more information.
Alaska is the largest state in the United States by area. It is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait. Approximately half of Alaska's 710,231 residents (as per the 2010 United States Census) live within the Anchorage metropolitan area. Alaska is the least densely populated state of the U.S.Source: http://en.wikipedia.org/wiki/Alaska