Roughboot was an early .31 fort. I was still a relativley conservative player back then, only having had about 6 months experience with 40d. Until that point I had not really ever inflicted massive amounts of needless killing on my inhabitants, either deliberatly or accidentally. This fort changed all that. Roughboot was protected by a marksdwarf keep, around 6 z's tall, 12 by 8, and made of rough granite. 20 Marksdwarves lived in the keep - observing through fortifications on the top floor, and training/living on the bottom floor, next to the hospital. It stood on the east side of a brook running though a flat woodlands. A dry moat with drawbridge allowed access for those I wanted in.
4 years in and I was at around 75 inhabitants, of which about 20 were children. Winter rolled around and a force of goblins and trolls arrived, and in far greater numbers than I was used to. Almost 30 bowgoblins and similar numbers of trolls. They were fought off, but not without the loss of some herbalists. My hospital filled up with wounded soldiers, and my inhabitants went about the job of cleaning up and gatehering the spoils. While they did so, I laid great plans for beefing up my defences.
A new underground chamber was dug, one end ramped to the surface, the other crammed with ballistae before turning through a series of corners towards my underground depot access beneath the old tower. The old tower was remodelled - drawbridge bricked up, old fortifications replaced with walls, and a new firing balcony added to overlook the access point to the ballistae chamber. Once all contruction orders were laid down, I went back to ensuring the orderly running of the fort. Some time later, a game log message pauses my game and grabs my attention - "A section of the cavern has collapsed!". I zoom to the scene, expecting to be taken to the caverns where some careless miner has carved a chunk away. Instead I get taken to the old tower, which is full of children ripping out walls, floors and fortifications, soldiers on duty, soldiers training, soldiers sleeping, wounded in the hospital, and dozens of temporary masons building the new platform and connecting masonry, or replacing the old with new brickwork.
Basically what occired was this: I had forgotten that the tower had a roof. In tearing out the old fortifications and firing platform, this roof had been left with nothing holding it up. Gravity did its thing and it went downwards. The falling roof went downwards filling the barracks and hospital and depot on the level below. In falling, it removed any support the new unfinished balcony had - it too fell away.
As the dust cleared, I surveyed the scene. Most of the demolition work was being carried out by children. Most were dead or dying, in what was left of the barracks, hospital and depot. My military was gone, suffering the same fate as the children - dead or broken from the fall or effects of cave in dust. The hospital, well, it was depressing. The already treated were surrounded by the victims of the cave in, most of my busy medical staff amongst them. One unharmed war dog was quite happly sitting next to his dying master who had a damaged upper and lower spine. On the surface, maimed and dying (or already dead) masons were scattered in a rough rectangle beneath where the firing balcony was going to be. I had lost 18 of my 20 troops, around 15 children, 8 masons, 4 medical staff, 8 dogs, a cat and 4 chickens. A further 9 died in a tantrum spiral before any kind of normality was returned to the caved in gatehouse. I didnt do much cleaning as it looked pretty cool, all trased masonry and blood - just flooring over points I didnt want enemies getting in at. I remember feeling guilty and finding it hilarious. This image of some badly designed tower being worked on, with one stone block holding the whole rickety assembly together, before some child pulls it out and it all goes down like some kind of jenga game.
The 25 to 30 survivors went on to die later that year when an ambush got as far as my workshops before being spotted.
The best part of the whole thing? There were elves in the depot. They probably did little to slow the falling bits of masonry and dwarves though.