Introduction to Grain Square: Grain Square was a place for grain trading in ancient times. Now it is a quiet small square at the east end of the main street. It is very close to the castle and you can look up at the scenery of the castle. The statue of Our Lady in the center of the square was erected by the Jesuits in the 18th century to win more Catholics. But to this day, Heidelberg is still a predominantly Protestant area. This is the starting point for the trip to the castle.