I’ve been wasting hours on Terraria (which is an awesome game btw) and here’s the result, my own castle (click on the image to get a full-size version)
This was all mined and constructed in-game using my trusy Molten Pick-axe, Molten Ham-Axe, Jet-Boots and Ivy Whip. My two boys helped me a bit too, especially on the mining (those blue dungeon bricks are damn tedious to mine!)
If you want to download the Terraria world file, here it is (zipped up for efficiency, make sure you unzip it before using it!):
N.B. Please be careful when copying this world file into your Terraria Worlds folder. Because it’s named WORLD1.WLD it will likely overwrite your own first world file unless you rename it!