Well, I found this one by accident while trying to make two layers of walls surrounding each player. If you first declare to have the starting position guarded by a stone wall, and then a palisade wall (order is important), the palisade will be put on top of the stone wall, creating a very cool double layer effect. I haven't done much testing, but it also seems that opposing forces might have to break through both walls to get to the city.
Don't know when/where this would be helpful, but it looks really cool.
- .... ..- .-. -.. .-.. ----- .----
.... --. / -.-. .... . .-. ..- -...
.. ..-. / - .... . / --. . .-. -... .. .-.. / . ... -.-. .- .--. . ... --..-- / .-- . / .- .-. . / .- .-.. .-.. / -.. --- --- -- . -..