What Are These Huge Concrete Arrows in the Desert For?...
During the late 1920s and early 1930s, the US Depa... ...constructed on the ground along the way as visual navigational aids for the planes flying the mail route. There...
http://www.neatorama.com/2013/05/02/What-Are-These-Huge-Concrete-Arrows-in-the-Desert-For/



