Which faction’s city do you like the most?

The most beautiful is definitely the Sylvan... but the others are also good, I especially want to note Haven, Academy, and Necropolis. Fortress is too bright for a snowy area, and Inferno and Dungeon are weak in architecture; the cities (especially at the beginning) don't look very good, although they look quite decent at the end... I can't say anything good about Stronghold.