Violentlash, my so-far longest running fortress, having existed for almost 28 years by now, has mostly had to deal with sieges. It hasn't brought forth any great constructions or such. But I've been doing some "research" into troglodyte and goblin mental states lately. (Stress-"research"...)
Stress Test Subject #11 (a goblin bowman caught in my garbage dump, among a few hundred goblin and troll corpses) has finally gnawed through the platinum bridge. I cannot explain in any other way how he managed to make the bridge below him disintegrate.
He has reached the "harrowed"-state and switches between stumbling around obliviously, giving into depression and throwing tantrums. (His stress level is at 571'139 at the time of writing this post.)
Considering that goblins are practically immortal, won't starve and that there should be no way for him to kill himself - unless he manages to destroy the magma inlet (raised iron bridge) or the door leading out of the garbage dump (forbidden green glass portal) -, experimentation on how extreme levels of stress affect goblins (and creatures overall) will continue. Further goblin siege remains will continously be added to his surrounding ... as will any other kind of garbage.
So,...I'm having fun torturing experimenting on a goblin prisoner.
Besides that I also managed to finally figure out a way for quickly emptying all the other goblin-filled cages I had without risking the lifes of my squishy dwarves.
A minecart-shotgun design, with a 10 z-level ramp, "dumping" the cages into a 5x5 room full of large serrated disc-weapon traps, which is connected to a small room where I station a war-trained cave dragon for the (naked) survivors, does the job of removing goblins/trolls from cages quite nicely without destroying the cages in the process; unlike my previous methode of just dumping them into magma.
I just wish I'd get some more interesting goblin sieges, all I get are goblins+trolls. Where are all those fearsome mounts I keep reading about?
Still not decided what big project to go for. I love watching the fortress work as it does though. Quite smooth for a 135 dwarf-fortress with tens of thousands of items.