Well, I should say that you ought to go East and have a look round. After all there is the Side-door, and dragons must sleep sometimes, I suppose. If you sit on the doorstep long enough, I daresay you will think of something.
- Bilbo Baggins
I'm really debating how I should rank the difficulty on this one. Its a bison tube that your looking for, and there is intermittent high muggle traffic. If you don't get the quote from above as a hint this may take you quite a while to find. On the other hand if you get the Tolkien reference this should only take you ~5 minutes.
Oh and I cannot forget to thank the Longbeard's for without some of their Dwarven influance this cache wouldnt exist.