Students in Finland will get together and jump up and down, trying to push a city into the sea.

In the U.S., Baseball teams have rivalries, not cities. Not so in Finland. Two Finnish cities, Tampere and Turku, have a long-standing rivalry.

Usually, the two cities' residents usually just joke about the other city. Some of the most popular topics are the state of the Turku River, the Tampere food, and the respective regional accents.

Since 1997, though, Tampere students have traveled to the market square in Turku. There, they jump up and down in an effort to combat the post-glacial rebound and push the city back into the sea.

(Source)