On the 15th of May 1248 King Erik IV of Denmark granted the Lübeck city rights to Tallinn. This was a significant event that allowed Tallinn to join the Union of European Cities. A town council was formed and shortly after Tallinn became a member of the Hanseatic League which saw it become a major trading hub. Many of the beautiful old buildings found in Tallinn's old town today were built during the Middle Ages when Tallinn's merchant community thrived.
Today we celebrate Tallinn Day. A list of events can be found here.