I like building 3d forts making use of ramps and localized stairs instead of just one big stairway and a bunch of branches.
Like instead of just a single large room branching off of a hallway, I can have more than one in the same space but on different levels. In my last fort the hallway going into my food production area of my fort branches off several ways. One ramp up leads two levels upward to an animal processing area, with butcher shops and a fishery with a ramp down to a pond right next door for indoor fishing (turtles, the pond is fed by rainwater from above) and large stockpiles for the meat and fish and cheese (any animal product that hasn't been cooked). Right beside that ramp is single ramp entry leading to the kitchen and still area, with large stockpiles for plants by the stills and farmer's workshop and some stairs up to the butchery area near the kitchen so that they can access the stockpiles above and stairs down to a level devoted entirely to plant storage. Next to those two entry ways is a ramp down, leading to the farm area - this one also has stairs connecting right near the plant stockpiles, so that plants can be carried right on up to the cooking and processing area above and seeds can be taken back down to the seed stockpiles which are alongside the farming area. The same pond used for fishing is also used to irrigate the farmland when needed, with the excess water being pumped back into the pond via a dwarf operated pump in the wall of the level above it, which serves entirely as a stockpile for plants (since I grow quite a few) and has stairs between the kitchen and farm areas.
Then my dining hall is across from this, and it has a three level very large cellar under it full of barrels of alcohol along with a single level stockpile above it full of cooked foods.
The residential area is built on a similar design. The hallways have ramps leading upward and downward and straight ahead, giving me 3 layers of rooms with only 1 hallway. I make use of the excess space where the hallways would be by enlarging the rooms or adding additional rooms onto them, making suites for the nobles with private dining areas and offices. Some of the rooms below and above have further stairs inside them going up or down leading to the offices or dining areas.
Looking at a single level of my fortress was rather confusing - you see hallways going off and just ending, with rooms through the wall in that direction seemingly unconnected to the rest of the fort. Looking at it from the combined perspective of all the z-levels lets you see all of the hallways connecting via ramps and stairs and such, forming a sprawling fortress where everything is branching off from the main entry hall, which is the only way in and out of the whole mess despite many of the rooms coming very close to connecting with the outside world (in some cases, specifically the battlements above the main enterance, they have fortifications to shoot out of yet the only way out from there is down back into the main entry hall). Every space in the big rectangular structure is used, with something or other always being under or above every room, although sometimes being quite distant from eachother in terms of walking distance due to it being part of a different branch (although those areas are places where you wouldn't want back and forth between, like food processing and the magma furnaces).
It's a fun way to build the fort
. Definitely more fun than just central stairway and branching rooms off of it.