After discovering what a massive nightmare jail cages are, I've decided that I'm going to start creating some unassigned 3x3 bedrooms with a chain in the middle, with all the comforts of home - even 1-tile booze and food storage areas, and using them as jail cells.
oh, now that's a good idea. I currently have a dedicated jail area, but I use restraints spaced in 3x3 cubes (so they can't reach each other if one goes berserk) and fill the free tiles with lots of little food/drink stockpiles.
My current embark is on a freezing/cold environment (one freezing biome, two "cold") with a frozen brook and a volcano. I'm in year 18, I've got lava running underneath the river and melting it, I've got my military all geared up in masterwork steel armor/weapons, I've got everyone a little bedroom with green glass cabinet and chest, so forth.
I've got three major projects I'm working on now, then the fort will be "done".
The first is to finish my internal waterfall. The whole fort's arranged around a central double-helix spiral rampway (there are single staircases to get from workshops to storage areas, but the bedrooms and dining rooms and so forth, central stair). I want to hollow a channel down the center of that staircase and drop a waterfall straight down the middle of the fort, draining into the caverns. Should fully automate dwarf bathing, etc. We'll see how it works out.
The second is to build a freeze trap in my front courtyard -- again, this one's mostly planned and dug out, but I have to dig all the plumbing etc. for both it and the waterfall at once, so it's complicated. Right now i'm placing the pumps and keeping the architect busy.
The third is building a ice tower up into the sky. The climate in the specific spot I want to build it (on top of the central stair, natch) is a little weird -- ice rocks melt at the height of summer, but cast ice walls don't. So now that the river's melted I've dedicated pond zones and I'm just letting my dwarves fill in the z-levels. At some point I'll need to do scaffolding, but for now I'm just filling in the natural slope of the mountainside. Once it's filled out I'll just use my standard dig plan for the central staircase and dig it out of the ice to connect it up with the main fort. OR a fire titan will show up and melt my tower. We'll see!