Here's one I happened across when looking for this particular piece.
As a kid, whenever my mom drove us to the Brickyard Mall, we'd notice this Highway to Nowhere. I thought it might have once been part of an expressway system and this was all that was left. When I got older and more cynical, we joked that it was a construction pork project. It turns out, there was a legitimate purpose to it.
This structure was located at 6650 West Grand Avenue. A curved driveway, supported on concrete pillars 40 feet above the ground, with no ramps. For most of the thousands who passed it everyday, it was an intriguing mystery. A Northwest Side prototype for the Skyway, perhaps?
The Grand Avenue whatsis was actually a relic of World War II. Built by Western Electric in 1943, it was a track used for testing mobile radar equipment. The location at the top of a ridge made it higher than any buildings for miles around.
Originally a wooden ramp connected the track to the ground. The mobile radar units would drive up to the top, then planes from Glenview Naval Air Station flew over. The data collected was used to determine the efficiency of radar, which was then a new invention.