Željava Air Base, Croatia
You will find the biggest underground military airbase airport of Yugoslavia on the border of Bosnia and Herzegovina and Croatia. The construction of this airbase started in 1948 and finished in 1968. Over the course of twenty years, SFRJ spent around $6 million on its construction. The airbase was used a lot during the Yugoslav Wars. After the withdrawal, the runway was destroyed by detonating explosives in pre-built spaces there. The Military of Serbian Krajina wanted to ensure that it would never be used again, which is why it was completely destructed in 1992. The explosion had been powerful enough to shake the nearby city. People continued to see smoke rising from the area even six months later.

Željava Air Base Croatia
Duga 3: Ukraine
The Duga 3 was in operation from July 1976 until December 1989. It was an over-the-horizon radar system that was once a part of the early-warning network of the Soviet ABM. They deployed two radars and deactivated them during the late ‘80s. It is interesting to hear that they all surrounded the Chernobyl power plant.

Duga 3 Ukraine