Okay, so I embarked in this one area that happens to be really freaking cold.
It stays below freezing year-round. There's a river, but it is also frozen the entire year, though I may be able to remedy this with lava. It would help if I could see more of said river...
Surprisingly, I'm not dead yet. Sadly, however, the game decided to start me off on the other side of the map from the section with anything of immediate use (a taiga area: trees and plants), and it's a pretty big embark. Nonetheless, if I survive, I have a plan.
This plan requires a source of water, preferably an infinite one (underground sea). I will construct a cast somewhere outside where I plan to put the tower. The cast will notably have a roof, and that's extremely important. I may or may not construct the cast with a floor plan; it depends on whether it'll be easier to mine out the rooms or build it (from my experience, freezing water destroys ramps, and it probably does so with stairs).
Next, I will make a covered tunnel that pumps water from my reservoir to the top of the cast without freezing, powered by whatever the heck I can make work. Most likely, that'd be elevated windmills, though I could place some waterwheels along my pump system to power it as well. Whichever works... In any event, also note that I'll have a floodgate where the water goes into the cast, so I can prevent backups.
So, once I have all this done, I'll pump the water into the cast, and close the floodgate once it's full. THEN! I will deconstruct some part of the roof. The water is exposed to the outdoor temperature and boom, water freezes into ice. Hopefully, anyways. Get rid of the cast (painstakingly) and you have a CAST ICE TOWER.
Why am I doing this?
Simply because I'm hoping that I'll be able to engrave the ice. >_>
Is this even possible?