What Are the Most Unique Accommodations You've Ever Stayed In?

Two places come to mind: Camp Jabulani and Château Eza.

Below are a few posts on each to give you a feel for each place.

http://snapshottraveler.com/stayovers/105-camp-jabulani-smack-dab-in-the-heart-of-elephant-country

http://snapshottraveler.com/destinations/50-getting-your-groove-in-eze-after-dark

I've never been there but the igloo hotel Kakslauttanen in Finland has to be on a lot of people's bucket list! http://www.kakslauttanen.fi/ 

I've stayed in the airplane suite at Woodlyn Park and at the Jumbohostel ... both super-unusual. 

Goldenwood Lodge in the Blaeberry Valley, near Golden, British Columbia in Canada has several comfortable teepees that you can stay in. http://www.goldenwoodlodge.com/  I used to guide small group adventure tours in the area and stayed there quite often.  The clients always loved it and wished they could stay longer. 

Love the look of the jumbo hostel!

You can stay in treehouses in Olympos and if you go to Lucerne you can stay in an old jail!

La Loma Jungle Lodge an amazing tree house type atmosphere in the rain forest in Panama.

In Coober Pedy you can stay underground - many houses are built into the ground, which is a good thing for a place that is so hot. I actually camped underground.

I haven't actually stayed in one of these, but have you heard about camping in a bubble in Montagnac, Allauch, Forcalquier, La Bouilladisse, or Puget-Ville? It kinda looks amazing. 

A cave in Cappadocia!  We slept like posh Flilnstones at the Kale Konak Cave Hotel. Amazing place and can not recommend it enough! For my review and tons of pictures see here: 

http://www.thislifeintrips.com/kale-konak-cappadocia-cave-hotel/

Any Bungalow in Ubud or any other city in Bali. Pretty nice places, some of them, with private pool.