In the back of the enclosure is a small waterfall. There is a green baseplate with the clear water section in it, and the falling water as a separate piece. The top of the water is covered over by a rock. The large rock section this is all attached to has a cave opening which is behind the waterfall. There are 2 of these big rock sections with a gate between and a rock over the top of that.
The large sections are the same but one is turned around the other way and doesn't have the water and so on. You can see the cave here.
Here is the gate that clips between the two sections. The rocks above it are a large piece.
This is a nice way to do the enclosure and it would be great to have a few more of these rocks.