The Marienkirche is one of the oldest churches in Berlin and well worth a visit if you're visiting…read morethe city! The exact date of the construction of the church is unknown, but the church is presumed to have been built in the 13th century. The church was Catholic, but was converted to a Lutheran Protestant church during the Protestant Reformation.
Within the church is the Totendanz ("Dance of Death") - a wall painting in the vestibule that was created at the end of the 15th century to commemorate the plague of 1484, which shows Death inviting people of all classes of society to dance. The wall painting was covered by whitewash but rediscovered in 1860. The wall painting is currently being restored.
The church is beautiful and free to enter (although donations for the restoration of the church and the wall painting are encouraged) - a must see if you're exploring Berlin or interested in European history or cathedrals.