The interplay between civilizations is absolutely brilliant, and it’s an absolute blast learning the ins and outs of each one. I could list the differences between civilizations all day, as many also have special buildings, units, research, and more. Then you have the Rus, who get major bonuses from hunting animals and accrue bounties. Meanwhile, the Abbasid Dynasty is focused entirely around their unique House of Wisdom building, and the only way to advance ages is by constructing buildings within the range of the House of Wisdom, thus expanding it. For example, the Mongols focus on ranged combat, get resources from burning buildings, and, due to their nomadic history, are the only civilization that can literally pick up and move their buildings.