From the publisher's website:
This set comes complete with 27 new exciting pieces that will add great water features and portable walls to your next Cavern setup. The pieces are fully hand painted, they are made of rock-hard polystone and they come in a custom-made cardboard box with a styrofoam insert for maximum protection. The set includes:
• Three Curved River Floor pieces
• Two Straight River Floor pieces
• One Dead End River Floor piece
• One T-Intersection River Floor piece
• One 4-Way Intersection River Floor piece
• Four Straight Cavern Portable Walls
• Four Curved Cavern Portable Walls
• One Dead End Cavern Portable Wall
• One Dead End Cavern Waterfall
• Four Hanging Stalagtite Opening pieces
• Four Skull Totem pieces
• One Crude Wooden Bridge
The River Pieces
These pieces are 4" x 4" and they look like the floors from the Cavern Set -- only with a waterway running through them! These pieces can be turned and linked in a variety of ways to make innumeralable riverways.
The Wall Pieces
These pieces are designed to work closely with the River pieces to make water-filled passages and rooms. When placed on top of a River piece you cannot tell that a Wall piece is not joined to the River piece. These Wall pieces can also be used freely in other parts of your caverns to form free standing walls or to close off openings in the walls.
Note: Sets that were pre-ordered before release included a bonus crude raft piece, where the raft was made from an old door.