How do you unlock new places on call of duty wold at war zombie mode?

In Call of Duty: World at War's Zombie mode, new locations can be unlocked by progressing through rounds and completing specific objectives. For instance, in the map "Nacht der Untoten," players must survive rounds to access better weapons and equipment. Additionally, in maps like "Der Riese," activating the teleporter can open up new areas. Players can also find and complete Easter eggs that may lead to unlocking further content.