On Bellevue Avenue is the International Tennis Hall of Fame & Museum. In here, you can learn about the history of tennis from it's creation to modern day. The most interesting part to me was seeing the kinds of clothes they were back in the 1800's and early 1900's. I don't think anyone would even consider wearing clothes like that these days to play tennis.
You'll also see all of the inductees to the hall of fame with an interactive exhibit to allow you to learn about their career. There are also courts here that are still actively used and can even be played on by you for the right fee, including lessons. Another very interesting portion is where you can see an indoor tennis court where the rules allow you to play the ball off the wall. This can also be played on for a fee.
For any tennis fan, this is a great experience. However, if you aren't a big fan of the sport, there isn't too much to interest you in a visit.