Introduction to the Holy Spirit Cathedral: The Holy Spirit Cathedral on the Market Square (Marktplatz) is the largest and most important church in the Old Town of Heidelberg. This is an ancient and elegant Gothic red brick building, built between 1344 and 1441, and has a history of nearly 700 years. The church originally contained the tombs of successive kings and electors, but they were all destroyed during the Grand Alliance War. The only thing left today is the tomb of the church's builder, Elector Rupert III. The interior of the church is very simple. Between 1706 and 1936, a barrier was erected in the middle of the church to separate Catholics and Protestants who were worshiping at the same time. Now, this is a Protestant church. There are many stalls selling souvenirs around the church's outer wall, which is also one of the traditional scenes of the market square.