The Clam Key. You will need to have solved Puzzle 9 (The Statue), a Master Builder, a Master Scientist, and a Tribal Chief. Once the statue is completed, a rough pearl will appear near the statue's feet. Have a Master Builder pick up the pearl - he/she will take it to the waterfall to be shaped. After the builder drops the pearl, drop a Master Scientist on the pearl to take it to the research lab to be finished. Then have the tribal chief pick up the finished blue pearl: the chief will use the pearl to get the key from the giant clam and will then put the key in the door. (As with the other key puzzles, the pearl will return to the last place it was located if a villager drops it before reaching their destination - they will have to pick it up again to complete the task).