Id love to see screenshots of your improbable fortresses.
I have a tendency to try and build in the most unlikely and often difficult places.
I usually search for the North most land, or North most forests, hottest regions, most evil, etc.
I admittedly suck at the game, and rarely last long, but this kind of challenge always feels so rewarding.
I’ve successfully built on glaciers a couple of times, but that was several versions ago and I have no screenshots. It helps to bring along non-grazing livestock like pigs. And spend any extra embark points on logs to make beds with.
Haunted biomes are the ones that always do me in right away.