Polygon? Hmmm,
This is the Don-2NP Pill Box radar station, part of the Moscow ABM system.
The Don 2NP large multifunction phased-array radariis an integral part of the A-135 Moscow ABM system. The radar, which has 360-degree coverage, provides support for GAZELLE and GORGON interceptor systems.

Further info here: http://www.globalsecurity.org/wmd/world/russia/pill_box.htm
http://www.globalsecurity.org/wmd/world/russia/moscow.htm
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