Hi guys,
I've opened a hole beside my base and found a exists cave. The hole is big to permit I go down with my tractor.
When I flatten the ground inside the existing cave, I got a BIG decrease fps rate.
And I think that's possible because if I flatten the ground from the peak, I made a second ground and more poligons are created, and it added with existing polygons.
I will try today, if I flatten the ground in lowest level of the relief and decrease polygons, if the FPS will be stabilized.