Caves in landscape

Is there a tutorial to make caves in mountains/landscapes in Rhino?
Or what are good commands to use for making caves?



In the past I used T-Spline to create a complex SPA landscape. So far I remember me I created a line fence and convert it to a T-Spline object. Also organic caves was easy done. Here I found some old screenshots and a rendering.


okay, sorry, i am going to look at that first and all the available tutorials

Nice! I am a student, so I can download T-Spline for Rhino luckily for free. It looks very helpful. I am going to try it!