We spent a whole day with the GPS trying to find some of the old missile silo sites here in Tucson. We found two, this one we could roam around and explore.
Not entirely sure what most of these things are but it was cool to check out.
The tube at the bottom must have been an entrance, it is filled with concrete but you can tell a ladder was in side of it.
Pretty fun day, the boys enjoyed the drive and exploring the odd sites. The grassy field picture is from a different site, but it was pretty closed off and you couldn't get close to it.
There were 18 of these things around Tucson, check out this link to see where they were: http://www.siloworld.com/390th%20SMW/390th%20SMW.htm
Hike In Saguaro National Park East: