As you’ve probably heard, the University of Minnesota has an extremely large (over 60,000 items!) Sherlock Holmes collection. They claim to be the world’s largest. Unfortunately you can’t just go in and tour the library. As a librarian myself, I understand their archival concerns and (probably) budget woes. But it’s still really fascinating and, as far as I’ve heard from other Holmesians, really worth it to set up an appointment to see some of it.