Cave Entrance :
1) Create the cave entrance at the door of the room. Make rock formations with large strips of wide craft paper that is crushed together then pulled open and hung around the door opening.
2) Use gray and black spray paint to add more color and stone appearance if desired. 
3) Add nature items like flowers, grasses and stones along the door entrance.
Cave Floor:
1) Lay craft paper or a tan sheet on the floor to serve as the cave floor.
2) Cover a chair or other furniture item to allow the small waterfall to be placed.
3) Add some rocks made from paper grocery bags
4) Include other items such as drift wood or dead branches, mat for a person to sit upon and a lantern.
River and Waterfall:
1) Choose a bed sheet, large scale paper or some fabric that is a blue color to lay on the waterfall location.
2) Add a blue or iridescent foil curtain to lay over the blue fabric as the waterfall and small ravine.
3) Add some foliage and flowers but limited since caves are dark. This would be a good place to add frogs too.
