Spice Up My Watchtower

[Jaxilon]

Ok, I had a few minutes to sort of show you what I was trying to say. This isn't perfect but I think you get the idea.

I created a scrap layer used to draw lines I could "save to a channel" to mark the 'square thingies' . That way I could select the high blocks and low blocks separately.
I created an overlay filled with 808080 gray and called it shadow. I next pretty much loaded the 'square thingies' with white and black alternating around the ring.
I then create a drop shadow for the basic ring of the tower.
Create another drop shadow after selecting just the high 'square thingies' and offset that more than the first shadow. That's what causes the shadow to have the up and down 'tooth' look (most noticed on the inner walkway in the SE corner of the image.

I know that's a pretty rough explanation but I'm hoping you already know how to do it.