How to Get the 'Iron Curtain' Achievement in Assassin's Creed: Revelations

Today continues an overload of Assassin's Creed: Revelations posts, so let's begin! This is a lengthy video guide that comes from PowerPyx to get the Iron Curtain achievement. What seems like a herculian task will only net you 20G on Xbox 360, or a bronze trophy on PlayStation 3. What gives, Ubisoft? 

What it boils down to, is that you have to do a perfect den defense without using a single canon. Like, your den can't be damaged at all. I've always been awful at tower defense style games, so this achievement would be a hard one for me to get. Anyone else out there awful at tower defense? Let's start a club.