This awesome New Zealand hotel built out of a hillside, and a defunct train and plane has three sleeping options:
“Sleeping inside a 1950’s Bristol Freighter Plane refurbished into 2 beautiful motel rooms.
“Sleeping inside a 1950’s Rail Carriage 3 room motel unit, which sleeps six.
“Sleeping like a Hobbit–underground with a circular window.”
(Thanks, Mark!)
Update: Jon sez: “This reminded me of a relic of the Iran-contra affair that was converted into a restaurant/bar in Quepos, Costa Rica.” How cool — I used to live pretty close to Quepos in a squatter/refugee village on the Nicaraguan border and the locals had lots of stories about disused Contra airstrips in the bush.