I have seen one, really , at the San Francisco Federal Reserve Bank. They probably don't give tours post 9-11, but when I was in High School my class toured the FRB there. I guess for most of us the most interesting part was going down in the vaults and seeing the money. They had a small exhibit with the large denomination notes, many of which are now on their website. They also carefully handed out and kept track of samples of counterfeit money for us to examine, and then made sure it all came back.
The largest note that most people will own is a $1000 bill, and even in heavily circulated condition they are going for over $1600 now. The $5,000 and $10,000's are quite rare, I believe on the latter there are only about 300 or so still in circulation that the Treasury has not collected. As a result they usually go for over $40,000 apiece.