Cache Opportunity: Giant Concrete Navigational Arrows in General geocaching topics Posted October 4, 2013 Seems like fun and apropos places for a cache. Anyone ever seen one / placed a cache near one? (Link to article below the quote.) In the 1920s, America began coast-to-coast Airmail service, but the pioneer pilots had trouble navigating the route, since navigation charts of the day were fugazi and you couldn't exactly pull over to ask a farmer for directions. And traveling at night, when it would have been most efficient, or in bad weather was impossible. To solve this Congress then funded these gi-normous arrow-shaped Airmail Beacons, some up to 70 feet long, to trace a route across the country. Navigational Arrows Article found here.