Red flashing lights atop tall structures - Model Railroader Magazine

 Another kind of light in the U.S. is the Aerodome beacon.  These would be found mostly on control towers, however if there is no tower that is tall enough, then the beacon is placed on the nearest tallest structure which could be a water tower or tall building. 

 If you want to get really creative, you make large letters that spell out the name of your town.  These letters were placed on the side of a hill or on the roof of a large structure (e.g. warehouse, grain elevator, etc.)  This was an aid for pilots to determine where they were.  If the letters were on a hill or field, they were made with crushed rock or concrete.  If place on a building, they were simply painted white or black.

Interestingly enough, the early pilots used the railroad tracks to determine where they were also.