Hanging Cross in Mainz — some thoughts

What is a hanging cross? Most may find a silly question here. I checked hanging cross in the Google images, and find an interesting hanging cross over the altar, which is the image below.

I happened to visit the Cathedral of Mainz in Germany. I found two interesting depictions in the church. The first one was the statue of risen Christ, about which I am not going to write here. The second one is…