Cool... I think this time, make it out of wood though... Sand's fine, but it's very labour intensive, and not that strong. Wood - we just plant trees, and continue harvesting. I have more to say about this, I'll contact you in-game.
Dude I don't know how you think wood is more labour inttensive, it is in so much less supply than sand and, with sands drop down quality makes it actually a lot tougher than wood - you can just make a tunnel in wood with 2 strikes. With sand you are not able to pass until the whole column of sand has fallen.
Plus - Sand is my desired material for that particular style kingdom, I have many uses of materials for many different types of colonies. Wood would look good for a Medieval english fort.