Towers that go from your bottom Z-level all the way to your highest Z-level, and on the topmost Z-level, roof off the ENTIRE map (short of the 5 tiles from edge limit). Blot out the sun, and have smoke stacks where to fuel them, have a 1x3 magma pool, then 2 z levels up, a pit with a hatch cover and toss sacrifices in. On the farthest tile away from the pit tile, build a smoke stack at least 5-6 Z levels up.
Build factories that house these that also use magma forges/furnaces for bonus points, also a giant 3d statue as mentioned, temples, and a combat arena, hopefully with a chained, wild dragon as the main event, with ground-level windowed box seats for dining. Perhaps decorative Miasma would be good too, on the surface level, paved roads of dark stone for the road itself, perhaps with 1x2 stripes of opriment, and white stone for sidewalk, paved roads as well. I think I'll add to this later, as this is just off the top of my head.
Edit: Giving it some more thought, there's of course, city defenses, only ways in through the outer massive wall being through some checkpoints, the outer walls littered with Ballistas ready to fire in the event of a siege, siege engineers training underground on some catapaults. Build a large park where the only thing built is a chair here and there, maybe a statue, and dirt paths. In a similar aspect, build a zoo, don't piss off the elves and import exotic species as much as you can. When you have 2 of each species, THEN piss off the elves.
Gotta have the meat factory where animals go to be slaughtered with the animal pens right next to it, build a huge shopping mall with lots of shops when you get the economy going, and instead of guard towers that are traditional and built and mounted in the ground, build some suspended ones from the city canopy (you'll still need to build ALLLL the way up there from the ground, but still). (On second thought, I don't think that'd work unless "chained" to a nearby tower by a walkway)
In at least one skyscraper, have water funneled into a fountain that is then taken to the very top and poured out to shower your dwarves with mist, and make sure you build a sewer system under your roads for drainage.
If you're up for modding, replace caps with fedoras, coats with waistcoats, maybe add in something that can be worn on the neck like a tie or necklace, maybe something that can be worn on top of shoes like spats.
Maybe chain fire imps to poles to function as lamps?
To really put the proverbial balls to the proverbial wall, take up not just a 3x3 tile or anything, but THE WHOLE REGION.
DOUBLE EDIT:
Also, sacrificial pits that are huge-scale are always nice. Like 4 10x10 bridges that all give out to make the hundreds of invaders plummet at least 30 Z levels into a pit that's completely laced with spikes that are all triggered by a single pressure plate in one of your most high-trafficked area. Great for getting rid of cats too. Make sure to add windows that dining areas can use to watch the carnage.