How to get direct access to a terrain's vertices?

I have been trying to find a good method to get access to a terrain’s vertices, but have yet to find anything that gives me this ability. Still reading the documentation, but if anyone knows what path I have to use to get there I would appreciate it. I am not looking for heightmap data I am looking for the actual mesh data that has to be somewhere… right?

The terrain meshes are not accessible, and aren’t meant to be, since there is no fixed number of them and they change at any time due to LOD. You can probably just use SampleHeight.