More than a decade ago the former state of Yugoslavia was the first communist country that was to host Winter Olympics in 1984, however after the bloody conflict in 1992-95 the country fell apart. During the war, in one of the battles as Siege of Sarajevo, which was the longest seige of a capital city in modern warfare, mountains of the surrounding city where used by both sides to maneuver, while using the Olympic stadium for storage of weapons and Intel bases.
For example the bobsled track became an artillery stronghold and there were some defensive holes, drilled by troops as you will be able to see in the concrete walls of tracks.
The ski jumps on example were also areas of heavy fighting and they remain unused today.
It’s still very dangerous to walk the mountains and forest around due to buried land mines that are still a great risk for any passengers.