Area Related FPS Drop

I'm using the PC version, running on Maximum and having a constant 60-90 FPS pretty much everywhere.

And here's the mystery. When I place the camera directly on top of my character (and look down) I have a massive FPS drop. Going from 60 to 10. This seems to be area related.

I've only tested this on New Girdania and Western La Noscea. In New Girdania I get solid 65 FPS, looking down actually increases the FPS. In Western La Noscea I get 50 FPS, when I look down it goes down to 10.

Any ideas?

Edit: After messing with pretty much every option I have found it to be Tessellation the culprit. However a new question arises. What does Tessellation exactly do in La Noscea? Because I didn't notice any particular difference, asides the FPS drop.

Tessellation does a lot to landscape but it can be pretty subtle. It's often in rocky terrain you notice it most where the ground is uneven. Instead of a flat texture with depth drawn on it creates variations in depth to create bumpy surfaces which are more realistic. You notice it more on cliffs and things I think or something like steps.