I had a day to kill when I got there, so I decided to visit the National Museum of Nuclear Science and History. There is a ton of great material and information at this museum. I spent a couple of hours there taking in everything I could. Following is just a small sample of what is there.
Model of the Trinity Gadget, the first Atomic Bomb.
Photos showing the sequence of the first atomic explosion.
Model of the plutonium core of the bomb. About the size of a soft ball.
A nice selection of extremely over priced trinitite at the museum gift shop.