just outside Chernogorks to the eastern side there is a rock formation at the coast where ground texture and ground collision do not match up. More specifically you can walk into the air between those rocks - though (zombie) corpses will fall to the ground.
- Legacy ID
(1) Move to Cherno
(2) Follow the coastline to the east
(3) Not far after you passed the name shield you will see the rocks to the right side
(4) Walk around there
The invisible ground collison can be quite steep at some points so be careful if you have to move quickly around those rocks.