Gilbert U-238 Atomic Energy Laboratory (opens in new tab)

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