Some of you might have seen these on Warhammer-Empire.
Basically I made this out of junk. The base is made from a disc of hardboard chopped out of a bit of scrap, and the walls are polystyrene cubes covered in a mixture of pva glue and fine pre-mixed DIY plaster. The floor is sand with a few judiciously placed bits of modelling gravel. The leafy plants are cut from thin styrene sheet and have stems made from wire, the ivy is an artificial natural sponge (huh?) and I'd imagine you're all familiar with model railway lichen, flock, and static grass. The flowers are bristles from a broom topped with flock.






The painting was simple - I sprayed the entire thing black, then picked out the rocks in a medium grey. When that was dry I made a very watery black wash and slapped that all over the grey, mopping and moving it around with a bit of rag. After that the stones were drybrushed with a lighter shade of grey, then very lightly highlighted by white drybrushing. Finally I used a very fine brush to paint some black lines across a few of the stones, following natural creases, then added the lightest touches of pure white on the highest points.
The interior was very similar. It was roughly painted a chocolate brown and then drybrushed with lots of lighter shades of brown. A few judicious spots of clear varnish gave the impression of wet areas. Dressing the thing was simplicity itself - a skull from my bits tin, foliage, etc.
The entire thing - allowing for drying times - filled up an idle weekend and cost ... ooh, shall we say, less than three quid, even allowing for the paint.