GIANT CONCRETE ARROWS
Pilots would approach from the back of the arrow, and if a change of direction was needed, the arrowhead would be bent to point in the new direction.
The middle of the arrow had a square platform for a beacon tower with a light bright enough for the pilot to see the next beacon at night. There were also red lights when there was no airfield, or green lights at an airfield. Most beacons were torn down to reuse the steel during World War II.
Arrows were originally painted yellow. As navigation equipment improved in the 1930's, the arrow system was abandoned, but people occasionally find them in remote areas.
Imagine flying a cross country air mail route with no navigation equipment and a primitive radio. That is what early pilots had to do until the postal service built a system of giant concrete arrows and beacons along air mail routes starting about 1926 (dates vary in different stories).
Bryan, Wyoming arrow.
Arrows often had another platform in back for a power source, usually electricity or acetylene.