Storage
During the fall of mankind, many places like this underground warehouse were converted into military bomb shelters. They had all the necessities: space for rations, safety from bombs, and could house hundreds of people, including both soldiers and civillians. This shelter, however, exceeded the elevator weight limit on the first group of people. The elevator broke, leaving very few survivors. The survivors assembled what they could, but they were trapped.
Just a map, not a game.