This historic site is in two parts. The main site is a deactivated underground command center from where missiles would have been launched. Visits are by tour. The other site is nearby, a deactivated missile silo that is quite eerie. Often unattended, you can ponder the doors that hid a rocket with over 300 kilotons of nuclear explosive power (the Hiroshima bomb had 13 kilotons). It's surrounded by mundane farmland and a few distant farmhouses.
Note that North Dakota still has active underground nuclear missiles waiting for launch orders.