Mc was in a big city before the apocalypse, there were like black stones around the city that you could find and claim and build your fortress around it (there was like game interfaces at the stone) and he knew where one was. The city collapsed into ruins I believe and  inside the city center there was a big shield at the center where a lot of civilians and the military gathered, Mc had found his friends before apocalypse and they were going around expanding in population by finding people in the ruins of the city