Create an isometric tower in Illustrator
There was a recent request for a tutorial on to creating isometric city icons in Inkscape. I'm not an Inkscape user, but hopefully some or all of these Illustrator techniques can be adapted.
Creating an isometric round castle tower with crenelations in Adobe Illustrator CS3.
Using the Rectangle Tool (M), create a rectangle of appropriate height and width for your tower.
Create another rectangle the size of the spaces of your crenelations. Make this rectangle a different color than the first rectangle so you can see it easily. This rectangle will be used to cut out the spaces on the top of the tower. Place it over the top of the original rectangle where you want your first crenel to go.
Using the Selection Tool (V), click on the second rectangle once, then hold down alt and start dragging the rectangle to a new position. While you're dragging, press shift to constrain movement to a straight horizontal line. When the new rectangle is in the position you want it, release the mouse button before you release alt and shift.
You now have a second small rectangle. Use Ctrl-D (command-D if you're working in MacOS) to make additional copies—each new copy will appear spaced exactly like the first one, so you don't need to guess to make each crenel identical.
Again using the Selection Tool, drag a marquee around all of the objects to select them all. Open the Pathfinder Window (Ctrl-Shift-F9). In the Pathfinder Window, click the Subtract button—the second from the left on the top row.