The RLS VNZ Krug (РЛС ВНЗ Круг) is located 1.3 kilometres southeast of the Duga radar in the Chernobyl Exclusion Zone. The Krug was used to provide real-time data on high-frequency ionospheric-dependent radio propagation (*takes a deep breath*). So if I understand correctly it's used to emit and measure a certain frequency.
There isn't a lot known about the Krug, at least not online, so I used Google Maps for all measurements and some Russian sites for additional images (and some guesswork :P). My Russian is pretty basic so I can't really tell you more about it.

Thanks to Roman_95 for the request and Wet for the trees!

https://www.planetminecraft.com/project/free-to-use-tree-rock-pack-over-350-variations/

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