Silverstone is not that flat. The current configuration doesn't help, but the most perfect layout from 1991 to 1993 featured a rise to Abbey followed by a downhill full speed through the terrifying Bridge corner. I would kill for this layout in AC, but at the moment it is only available in Geoff Crammond's F1GP.
Monza is not flat either. There is a downhill under the old oval bridge, that rises up towards the back straight to Parabolica.
Albert Park is seriously flat. I've been there 4 times, it is as flat as a witch's tit.