I've posted this before pre release but I think Venice would be fun. All the canals have dried up leaving catacombs behind that the fallen/hive/both have further excavated (similar to the moon just less drastic). This adds an extra vertical layer that could absolutely change gameplay. Evasion and stealth become and option and a third level of second story buildings falling apart could be very exploitable. Add all of this up and what you get is a very explorable and multi faceted pve and a highly competitive and versatile pvp.