I have been thinking about creating an experimental game that is set primarily in underground caverns, tunnels, and so forth. I've experimented a lot with games containing terrains and skies and so forth, but haven't done anything involving underground situations. I've seen games with underground locations that consist of square or round tunnels and so forth but I'd like to create something more natural, like caves that have formed naturally or been dug into the rock in such a way that it's natural looking.
My first thought is to model it using a 3d modelling package like Blender to create a mesh of the caverns.
I don't know if this is a suitable way of doing it, for performance reasons, not to mention memory usage and rendering, etc. I thought I'd ask for advice on the forums here and hopefully someone can provide links or suggestions on this topic that I can investigate and learn. I'd like to know what options are viable so I can research and learn and make the best choice for my project.
Further details if it helps. I'm currently using Unity3d but I've got some experience with a number of other engines as well as creating my own projects using c++.