Caples Track
[New Zealand, 2012]

Okay, I give up. I really have no idea why there's a door (complete with bolt, padlock and "please shut" inscription) in the middle of the Caples Valley, two days' walk from the nearest road, house or town.
Caples Valley, by the way, is a less-frequented alternative to the busy Routeburn Track, linking the road to Milford Sound with Lake Wakatipu.