I have a large tower, 24x24, roughly circular. It currently reaches up to cloud level (roof unfinished), and has a shaft running down the middle, at ground level it continues down into the ground, which I am going to dig down to bedrock. There's also a pool outside the tower, with a glass bottom and a large greenhouse underneath. Out from the tower will be plenty of rooms and corridors, currently planned are a temple (aboveground), a new storage room, and a hall for a nether portal.
Going southwest from the tower is a diagonal skybridge leading to my spawnpoint, on the other side of a small lake/sea/bay/whatever. In the middle is a tower, reaching from the ocean floor, where I'm planning to build an underwater house. On the other end of the bridge I'm planning a small castle/fort with my spawn point inside it.
That's just what I have planned currently, I'm constantly coming up with new spontaneous ideas (for example, the pool/greenhouse, which is the coolest thing I've built yet)