A whole range of new improvements helps these cities develop. All of the changes drastically affect strategy. Civ vets, throw out every easy way to win you thought you knew. The new pieces are deviously nice. Units like televangelists and corporate franchises can drain portions of enemy gold or production and transfer it to the player's civilization.
Later units can drop from space onto unsuspecting enemy cities.
Eco-terrorists and Infectors wreak havoc on enemy landscapes. A quick read through the manual should be enough to help players get a sense of what they'll have to do to win. For instance, all caravans are camels. More serious problems abound. Especially on the easier levels, the player's civilization advances at an astronomical rate.