It's pretty much like SimCity, but it doesn't play like SimCity.
You start by looking at an Earth-like planet. You'll have to decide where you want to begin building your city. This is important later in the game, as you can actually trade goods with neighbouring cities. In Multiplayer mode, those cities are actually controlled by other player from around the world. This is interesting, but requires a monthly fee.
When you've find a suitable location for your metropole, you can start laying out zones, like in SimCity. There are Residential zones, Commercial zones and Industrial zones. You can specify which type of Residents, Commerce or Industry may build there.
Once you start growing, you can build highways and railroads and connect to other cities.
And the best part is: the zoom level. You can zoom all the way in to street level (think Google Street View). You can also fly around like noclip mode.
This has serious screenshot making potential.
All the information above is from the many video's i've watched on the official Cities XL site: http://www.citiesxl.com/
Here some screenshots: Edit: Fuck it, im not going to get this game.
Interest.Lost = [blue]True[/blue]