I've played around a lot with caves and the best I've come up is your solution: a negative symetrical lattice and a positive cube. I generally use a square edge and the painted desert texture. I also like the mordor fractal map slightly smoothed to create the lattice. I then add either a small, weak radial light or spotlight and link it to the camera position. Water added to the lower part of the lattice works well. Even though the lattice is symetrical, it generally doesn't look that way in a rendered scene. I've also linked several lattices together: my only problem is the point of merger is too sharp (would be helpful if I could merge the landscapes so the polygons are smoothly linked). Rich