I don't know whether perhaps I am doing something wrong, but even after having disabled every conceivable option in video, whenever I move over a large city, the game's fps falls to one-digit figures. On a E8400 CPU with 4GB of Ram and a Ati 3870 0.5G. Divers are updated. Is it supposed to run like that on such a machine? It runs even Crysis on medium more than decently (though what a boring game that is...), so what's the matter here?

It appears to be directly connected to the amount of objects represented. Can the city buildings be simplified somehow? Because I otherwise wouldn't want to have to play in the cloth map view all the time (not that it would run significantly faster anyway).