I've created this image in Blender. There is no photoshopping done. I had to tweak lighting, layers, and textures to get it go behave the way I wanted as a playable battlemat. If you print it out at a scale of 1" = 5 feet, the interior of the castle room should be 6" for a 30 foot diameter room. The walls are 10 feet thick (2"). The staircase is 5 feet wide (1"), plus arrow slits. That funny little room to the right of the staircase is the garderobe. It would actually protrude from the castle wall so you could dump your dump, if you know what I mean.
|Castle Tower, 30 foot interior, 50 foot exterior|
The little square in the upper left is a fireplace. I've shown light from a torch to either side of the door, with light coming in the arrow slits and the big window in the room. My goal was to indicate shadows where a thief might hide. For instance, if a guard were coming up the stairs, a thief could potentially hide in the lower right arrow slit space, and the guard walk right by him. The garderobe is also a good place to hide, as long as that isn't where the guard is going!
Note, the only part of the tower that is wood is the floor. When the tower deteriorates, the floor would be the first to go. When all the floors and roof rot out, you have an open space the full height of the tower.
Also note that the large window ledge is 10 feet wide, and about 7 feet deep. That is virtually a room unto itself! Wall construction would have been a course of stone on the inside and outside of each wall, with rubble in the middle. I've made this rubble section 5 feet wide, which is plenty of space to hide a secret passage.
The funny area to the outside of the wall is supposed to be the tapering of the wall outward at the bottom.
Don't count that as part of your 10 foot wall thickness. Enjoy!