Experimental Breeder Reactor-I

For better or worse, nuclear power plants can be found the world over. But they all got their start from Idaho's Experimental Breeder Reactor No. 1 (EBR-I), the world's very first atomic power plant, which is now a nuclear museum where anyone can simply waltz in and see the inner workings of splitting atoms. 

EBR-I first powered up in 1951 to provide juice to four symbolic lightbulbs in a test to see whether usable electricity could actually be culled from a nuclear reaction. The experiment was a success, and the facility went on to power its whole building with nothing but its toaster-sized nuclear core. With the breeder reactor (a type that produces more fuel than it uses) a proven concept, it was only a few years before working nuclear reactors began popping up around the world.

The EBR-I continued to burn until 1964, never acting as a public plant but instead as a test bed for experimenting with the new energy source. When the site was decommissioned it was turned into a museum devoted, essentially, to itself, and the history of nuclear energy in general. Visitors can step inside the control room with its banks of strange vintage buttons and dials that once could have caused a national disaster, and get up close with the turbines that once ran off the steam of giant fuel rods.  

The museum provides the rare opportunity for the public to visit not just a historic facility, but a space that is generally kept off-limits for obvious reasons.