I would like a mountain structure m...

I would like a mountain structure made from stone. It should have a cave like this image. It should not be taller than 65 blocks. Additionally, it should not be cuboid. It should be conical with a flatish dome on top. There should be some dirt and grass blocks on the top of the mountain and occasionally on the mountain side where things are flat. Otherwise, all stone. dimensions to work within are 128x65x128.