I paved the sky.
Not ALL of it, mind. I got bored of it due to low FPS, but I'd paved over the goblin slaughter area, so nobody puked grabbing the clothing and armour.
I also made a magma moat. In the same fort as the paving the sky. Filled in installments, pumped up into a holding tank of sorts, and gravity-fed into the moat proper, with outlying regions fed from the moat by walled pumps and gravity feed stations, all accessible through causeways edged with fortifications for archers.
This was also a 200-dwarf fort, fully functioning. Few idlers, but mostly due to busywork thanks to the post-scarcity nature of it and having actually cleared the goblin clothing to a point where it WASN'T a constant, ongoing issue.
There was even an outlying archery tower covering the outside-the-map low desert plains, built over a natural hollow in the ground.
http://skorpychan.deviantart.com/gallery/#Dwarf-FortressVisual Fortress shots of it, before the sky-paving was started. I posted those because they were just plain artsier, and didn't have a huge grey mushroom.
(And yes, I uploaded the save for someone to cave the lot in. It crashed their computer trying to process it.)
I have also converted an earthen hillside into a stone strongpoint, and built a system for dropping magma onto the surrounding grassland in order to ignite it, comprising of a naturally-fed small magma moat, and a system of pumps and storage tanks. Of these storage tanks, one is actually a murky pool, drained into the magma moat, mined out, re-walled larger, and paved over. Others are entirely constructed, with roofed magmaducts heading out to the entrance, the main dump pile, and the chosen ignition point.
Project suspended due to low FPS, poor understanding of how fires start, and the discovery that the fire would kill the FPS even more than the issue it was solving.
The issue was the decade of goblin clothing I thought was holding up FPS.
It turned out that the POWER for the magma ducts was the issue. That, and the huge axle systems transferring power to various pumps, the levers hooked to gear mechanisms, and the magma flows themselves.
I also managed to hook a swampy map covered in murky pools into a single aqueduct, fed from a brook.
Then hooked the whole lot directly into the brook, to make the water fresh.
A year or two later, I pulled it up on D11 with a non-zero FPS to try and pump a hole in the water to wall it off. I failed.
I have a long attention span, and I dislike the early game.