Where is the oddest location you have built your layout

My current and most recent previous layouts were and are both in the basement. 

Previous to that, we were looking at a house that had no basement, and I almost said no, until my wife mentioned that the den would make a great train room. And it fit the 8 by 16 I wanted.

But the most interesting location was in the kitchen of our first house. 

I built a tri-level HO layout in a 24' RV trailer back in the mid-1980s. (Stripped out the furnishings, re-sheathed the walls, etc.) Once the layout was functional, I ended up moving it with me to another state without issues. Kept the layout for a total of about 11-12 years. Worked out pretty good for being portable.

Hospital...  years ago Dad had to have an emergency surgery. Sitting with him that night,  I was looking at his dinner tray that rolled up to his bed... went home and built a frame about 20"x30" out of blue foam that would fit on top his dinner tray. Put down a N scale kidney shaped oval with a siding, carved a creek for 2 bridges, and roughed in a mountain. Took it up to the hospital with some trains and some plaster, a couple of buildings, and we worked on it and ran some trains the next couple days while he was there. He still has that little layout today...