Cities Skylines is a popular city-building game that allows players to design and manage their own city. While the game does not have an official multiplayer mode, there are mods available that allow players to play together. To play Cities Skylines multiplayer, you'll need to download the Multiplayer Mod and install it. Once installed, you can create or join a multiplayer game session and invite friends to join you. You can work together to build and manage your city, or compete against each other to see who can create the most successful city.