Publisher's blurb: The Cavern-Tunnel Passage (small cavern) group of Naked Geomorphs contains 12 tiles, each with one two-position opening (CD) and a connected tunnel opening (T), with the three remaining positions filled with rock (R). Sets A, B and C are completely interchangeable. I.e., tile M1B can be replaced with tile M1A or tile M1C, without changing the basic structure of your map. Set B has broad passages without narrow restrictions.