Well-designed scenario and it was great fun to play. The threat of invasions keeps you constantly on your toes and you can't just expand your city without planning for a defense first. The city is well defended with towers but when I expanded west, I used a maze of lion tamers instead to cover a bit more ground and also to provide better cover so I don't have to transport more troops across the map every time there's an invasion.
I broke a usual rule of not relying on rescue loans when I started up the defense quickly to deal with the 2 early invasions. In hindsight, I probably could have managed without it if I had micromanaged the starting funds a little more, maybe delayed building the military academy, and just started with wooden bridges first to connect the Road to Rome. Anyway, I included an early save so you could see how I set up the defense against the first attacks. The other save is right as the last immigrant settles in. Culture rating will reach the required 60 in the following year.