As per the description on the main page, "Travian is a browser game featuring a world with thousands of other real players. One begins the game acting as a chief of a tiny village."
It's a simple, slow-paced strategy game with the goal of developing one's own village into an empire. The language learning aspect comes in with regard to the fact that the game is interactive and has versions in a large variety of languages. Not only is the game's interface in the language... but all the other players are fluent speakers which gives you the opportunity to interact in the language you're learning. Players can send messages with one another and the game is in general fairly social.
Aside from the interactivity, the interface of the game is also a great way to learn. To show you what I mean, here is a screenshot of the game's Swedish version:
So as you can see, there's great vocabulary to be learned: words like marketplace and raw material, many basic verbs such as "buy"/"offer", and the names of the game's resources: clay, wood, iron and wheat. And this is just one small snapshot of the game's many features.
Learning how to play the game via having the interface in another language is a great exercise. And of course if you can't understand something you can always check the English version (or whatever version is your native language).
So anyway, I hope you all start playing in the language you're learning!