As for the heightmap, I've looked at the mountain range and its pretty close to the altitude limit, but a heightmap will give a birds eye view of the area.
Does anybody know about making elevators in minecraft?
The sign in Spawntown about a suggestion for an observatory gave me an idea (besides, I like astronomy) to make one and other people would be welcome to build theirs in the area, however, it hasn't gone beyond the conceptual stage yet since I haven't decided where to build one.
I do have various other ideas though, so it isn't the only project I have in mind.
Also the island up north was a collaborative deal, everybody did their part, although admittedly you were the leader there and set up the underground base camp.