WEEK 34: WIKIPEDIA'S MULTIVERSE
The Wikipedia you know is just one of nearly 280 Wikipedias in different languages. Put them together and you have more than 35 million articles edited 2 billion times by more than 50 million separate users.
The English Wikipedia was the first, it's by far the biggest, and the most active as well. Five others can be considered top tier: German, French, Spanish, Russian, and Japanese. The rest have fewer of everything, following the familiar long tail curve (although there are some odd exceptions).
You might think Chinese would be one of the largest, but China's government has encouraged homegrown alternatives so in fact Wikipedia is just the third most popular Chinese online encyclopedia.
Fun fact: once there was even a Klingon Wikipedia, until the more serious-minded prevailed, and it was moved elsewhere. (It is still bigger than the 8 smallest Wikipedias.)