when to travel from spawnpoint by boat to the harbour, you should be in the southern section of those mountains, both the entrance to the cavesystem and the zombie survival fort studio are located in the/from northen side of the, so just fly to the other side. I had it before when i started as a survival but after using toomanyitems it somehow became creative.
A lot of work needs to be done there, use on whatever purpose you can think of. The cavesystem can also be for it to fit as co-op survival, just random idea.