Everyone has their own ideas of what's important and why. I'm curious what 10 tracks make your list and why? Here's mine in no particular order.
Daytona International Speedway - The Daytona 500 and the Rolex 24
Indianapolis Motor Speedway - The Indy 500
Mount Panorama - The Bathurst 1000
Le Mans - The 24 hours of Le Mans
The Nurburgring - Public access to a race track
Circuit de Spa Francorchamps - It is just an epic track hosting a number of prominant events. I believe it is also one of the 4 oldest tracks on the F1 schedule.
Monza - Audi apparently tests there for high speed and F1 has special aero bits built just for the speed at this place. Also another one of the 4 oldest tracks on the F1 schedule. Plus Ferrari is a big deal in the world of motorsports in general and this is sort of their home. I realize that's technically not THE Ferrari test track, but it is currently THE Ferrari race track as far as I'm concerned.
The Top Gear Test Track - while there isn't any actual racing done there that track has probably exposed more people to the idea of motorsports in the last 10 years than any other track... in the world.
Silverstone - Two reasons. Besides the previously mentioned bit about F1 history as one of the 4 oldest tracks on the F1 schedule among all the other major races they host it is also the home of the GT Academy competition. A competition that has put one of their young drivers in a Red Bull single seater among other careers GT Academy has launched.
Last but not least and perhaps most importantly... your local track. It is the easiest place for you to get involved in racing action. It is probably the best place for you to go to get some of your own experience as well. If your local track didn't exist there would be significantly less interest in motorsports as a whole.