Multiplayer is a newly added and important feature of SimCity. It allows different players to interact with each other in the same space (regions) in many ways, including selling water and sewage processing, volunteering police cars, fire trucks and other vehicles, trading commodities such as oil and more, all of which are voluntary. There is involuntary happenings, such as crime spreading from city to city, modules on city halls providing benefits regionwide, pollution floating from place to place, and people moving from city to city to work, learn and even be tourists.
Multiplayer also occurs out of regions. Prices can be affected on the global market by various regions and cities, and people will immigrate and emigrate to and from the region. Competitions run by Maxis, the developers, which are conducted between cities and regions, are also a sort of multiplayer.
SimCity 2013 is the first one in the franchise to include multiplayer in such an integral spot, and arguably, at all. The previous ones were all located in their own little land, which interacted with a generated world outside its borders, and only one player could access. This is why the developers claimed that always online was needed; no city exists in its own little bubble. However, this requirement has driven away many fans of the franchise, and caused great discontent; furthered relevantly by the online servers often being down, rendering the game unplayable sometimes, and irrelevantly by the small plot sizes.
Great Works
Great Works are one of the main features of multiplayer, along with trading and overall cooperation. They are large structures constructed on special plots which cities can't be built on, and which provide various boons and benefits to the region as a whole, meaning the cities working together is often required to achieve it, though the benefits are great.
There are four Great Works; the Arcology, International Airport, Space Centre and Solar Farm. They all cost a lot of money and many varied resources.
The Arcology is essentially a sort of biodome that provides for itself, meaning that no maintenance is needed, and is able to function by itself independently without outside help. It provides a large population boost to the region in form of immigrants, tourists, etc. without having to provide for them when the go home.
The International Airport is fairly self explanatory; a very large airport, which brings in and out many passengers and cargo, which will all be good for trade, tourism, growth, and much more.
The Space Centre is probably the most interesting of the four; requiring research in the university, it creates a launch site for a missile to go into outer space.
The Solar Farm is exactly that; a great big solar farm, that provides masses of free energy to the region.
