Gilbert U-238 Atomic Energy Laboratory

If you think the link is cool, and you wish you had even one piece of it, you can build your own cloud chamber at home:

http://www.symmetrymagazine.org/article/january-2015/how-to-...

The relevant clip from the last episode of QI.

https://www.youtube.com/watch?v=ipFIxrsYSxs#t=3m40s