Actually it’s called the LSD castle, but I just liked calling it the rainbow castle.
At first glance this is a relatively simple design, but take another look. Did you notice that the minifigs are color coördinated with the castle? And they eyeballs on the walkway into the castle?
And then look at the architecture of the castle itself. There’s some great detail work on the tower. Oh and what about the microfigures in the gateway?
Source: Flickr — Simon Schweyer