First I start out with cubes in Hexagon, arranging and sizing them to match the photo. As you can see, I'm not aiming for the same level of detail or an exact copy, but want my castle to roughly look like it. The roofs are also cubes, but by selecting the top face only and scaling that one down, you get the roof shape.

 

The little figure is important as well, it's used as a reference for the scale. In this case it's the toon generation figure from Poser.

Artwork and 3DToons items, create the perfect place for you toon and other figures!

http://www.renderosity.com/mod/bcs/index.php?vendor=23722

Due to the childish TOS changes, I'm not allowed to link to my other products outside of Rendo anymore :(

Food for thought.....
https://www.youtube.com/watch?v=pYZw0dfLmLk