I downloaded a design for a hall and tower atop a hill from Thingiverse, which unfortunately I can't find now to link to. It's a pity, since I can't illustrate how it's printed as a single piece, but it doesn't look like that in the painted version.
So, then: masked the base and roof, primed the rest and hit it with stone-textured paint. Painted the "rock" with moss-texture paints, filled the base with sparkly blue ink, and did the top with aged copper. The castle is hollow and sized quite comfortably for a battery-powered tea light.
And I'm acquiring quite the collection of nifty little experiments which I have nowhere to put and no clear thing to do with them. I don't have room for all this stuff!