Monster Taboo

After the disaster, the earth was devastated, shrouded in radiation, species mutated, monsters rampaged, and civilization disappeared. There is not much left of humanity in this apocalypse. In order to survive, the surviving people built a barrier on the ruins to block the monsters: the 'Black Wall'. In the end of the world, where should humans, who once were the absolute masters of the earth, go now? How should they survive?