The developers at Turn 10 Studios have to do exactly that for the upcoming Forza 4 video game. It's an interesting process, and Turn 10 has released a video showing us how it's done. It highlights the nearly three-mile-long Hockenheim circuit in Germany, which features 13 turns and plays host to both the German Grand Prix and DTM events.
We won't spoil the track-creation magic for you. Instead, click past the jump and let Turn 10 demonstrate how it happens.