Recalling an era when the word 'atomic' conjured modernity and mystery, the Smithsonian-run Atomic Testing Museum remains an intriguing testament to the period when the fantastical – and destructive – power of nuclear energy was tested just outside of Las Vegas. After visiting the museum, it's almost possible to imagine that during the atomic heyday of the 1950s, gamblers and tourists picnicked on downtown casino rooftops while mushroom clouds rose on the horizon. Don't skip the deafening Ground Zero Theater, which mimics a concrete test bunker.