Back in the 70s, amateur radio enthusiasts around the world began hearing a sharp, repetitive tapping noise at the 10Hz frequency, which disrupted communications and could occasionally be heard over telephone circuits. It was dubbed the "woodpecker" signal, and this was the cause of it: a Russian over-the-horizon anti-ballistic missile system called Duga-3, which could give early warning of missile launches.The antenna was switched off back in 1989, but still stands, abandoned near Prypiat, just outside Chernobyl in Russia.
Artificial Owl has a whole heap of amazing photos taken both of and from the tower, and is well worth checking out to get a proper perspective of just how large and impressive this radio antenna actually is.
[Artificial Owl - Thanks Kaan! Originally passed on to me by "crisis and da shewz massive". - Kaan]