New F1 tracks and top speeds

Today I saw Grand Prix. The old Monza track was amazing. A race with todays F1 cars would replace the Indy 500 as the greatest spectacle in racing. Would it be possible to race on it again? I know its been modified for safety reasons since Von Trips died in his Ferrari in 61, but it would be an amazing race. A really cool racetrack would be a complete oval that you never had to brake on, and it was all the same angle no curves, just a massive oval, like an egg. It would probably come out at 20 miles or maybe more. Is there some kind of speed limit for racetracks today?