This could be the final zombie map, as this is where the zombies were created. The offical Zombie back story could be explained here in the Solo campaign cut scene.
Der Riese means "The Giant" in English and was the name of a supposed Nazi Research facility;
It is a secret Nazi Research facility in Poland.
There will be new Pack-a-punch machines, which can upgrade your weapons.
There will be teleporters.
There will be 10 more achievments/trophies.
The Wunderwaffe DG-2 will return.
The Hellhounds will return.
The words The Giant were said in the radio message, as the person said that the "Giant must remain at all costs", possibly meaning that the Giant has been taken over by the Zombies.
In reality, a factory named Der Riese is believed to be where the Die Glocke 2 was made.
Just like every zombie map, Der Riese might contain features from multiplayer maps. Der Riese is set to be in a factory meaning, features from Corrosion (which is based in a factory like area,) might be taken and put into this new Zombie map. Also, the factories/warehouses in the map Roundhouse might be used as well.
Because the map's name is in German it can be assumed that this is a Nazi Zombies and not Imperial Zombies map.
The monkey bomb and bowie knife are the new weapons in der riese