Right now, every city everywhere in the world is built along the same lines. Obviously, in the long run it would be neat to see variations in local architecture, like we have in the real world -- so one civilization might build huge pagodas, another one might go for blocky towers, another might build round huts or whatever.
I'm pretty sure the basic idea has been brought up, at least. But let's try and list some interesting ways to make differences in architecture visible in ascii -- that's an important factor, too. Practical ideas for how architecture could vary from civilization to civilization, in other words.
In Fortress Mode, we obviously can't force the player to build according to a certain architecture -- but dwarves could 'prefer' their native architecture, and could have thoughts about the area being "too cramped" or "too open", say, if their culture prefers this (obviously this would be for dwarven definitions of cramped and open, but there is still room for variety.)
Some ideas to get started:
* Building height, of course.
* Construction material. Straw vs wood vs stone. Some might use dirt floors, or stone only for the floors.
* Decorations. Some cultures might put statues outside every building for good luck, or engrave each of them. Some might have signs outside of their stores; others might not.
* Shape. Square vs round. Sprawling (with rooms sort of haphazardly added on) vs. compact.
* Wide, open streets or scattered structures vs. tightly-packed cities and towns.
* Overhead connections between buildings, or underground ones.
* Ramps vs. stairs.
* Window frequency. Some civilizations might even use glass; others might just have fortification-like arrow slits on all their buildings.
* Number of doors. Some might have only one small entrance; others might have double-doors, or many ways in and out.
* Depth. Some civilizations might build cellars, while others don't.
* Ponds; some civs might have them indoors, or just outside their doors.
* Pets; some civs might have chained pets outside their structures, or just inside, including guard dogs and the like.
* Size. Huge buildings vs. small ones.
* Balconies, both external and internal (the current inn template always has a balcony, say. Some might have that, others might not.)
* Some civs might divide structures into internal rooms; others might have one big mead-hall style affair for most structures.
* "Traditional" layouts for specific kind of structures. For instance, an entire civilization might share one traditional layout for all their temples, or most of their inns. Smaller sub-components and templates could have traditional layouts, too (so you see repeating motiefs -- like the layout of the roof, or the location of the stairs), though they might vary from instance to instance.
* How do they treat the surrounding area? Some civs might flatten the whole area before they build; others might build structures directly into the hills, and have streets that rise and fall over them -- or which tunnel through them. Some civs might clear-cut all vegetation for a wide distance around their towns; others might let it grow right up against their houses.
* Rivers. Right now, while towns often build generally near rivers, they don't put them to much use. Towns should have their own ways of building bridges over them; some civs might build overhanging buildings over the river, or even into the bridge itself. There should be mills and such in towns, too...
* Canals. A few cities with a water source might actually build canals, especially in swampy ground.
* Stilt-buildings. Related to canals. Used in the real world in swampy or flood-prone areas, the buildings are raised up on columns like 'stilts' to keep them dry, with a staircase leading up and in. Often with walkways between them.
* Other motiefs -- smaller structures people like to stick on to their buildings. Minuets. Little towers. Domes. These might be worked into specific types of structures (so all your temples have a dome and a little tower, or a huge spire), or they could appear randomly on buildings throughout the civilization.
* Multistory buildings might vary by floor. For instance, some civs might traditionally put few windows or other openings on their first floors, to discourage burglers, but have them on the upper floors.
* To keep things interesting, there should be some exceptions to the rules -- a foreign merchant might set up a structure using their own traditions. Local tolerance for deviations might vary from civ to civ and from city to city, so there could be some big trading towns that are dazzling arrays of clashing architecture, while small towns might be mostly monolithic.