A tiny tunnel was constructed that served as the entry point to the city through which supplies were transferred (and a few thousand civilians fled the city): h

A tiny tunnel was constructed that served as the entry point to the city through which supplies were transferred (and a few thousand civilians fled the city): https://en.wikipedia.org/wiki/Sarajevo_Tunnel https://en.wikipedia.org/wiki/Sarajevo_Tunnel It went underneath the airport (controlled by the UN at the time) and is now often referred to as the "Tunnel of Hope". Definitely not big enough to stand upright, but the city was fortunate enough that the Serb forces never quite figured out where the entrance is (a private home that looked quite ordinary from the outside).