Shoshone, ID

At the same site as the Shoshone Bird Museum of Natural History is Mammoth Cave, a lava rock cave used by Stone Age settlers. It was discovered by the second Olsen in 1954, who used it to grow mushrooms, and later opened it as a public attraction alongside his museum. In the 1960s the government designated the cave as a Civil Defense Shelter. In the event of Soviet attack, citizens could take refuge in the cavern, just as settlers long before them had. Though the threat of nuclear attack has faded since then, the dirt road leading to the museum still bears the name “Mammoth Cave Civil Defense Shelter Road.”