Which cathedral that features the Gero cross is a renowned monument of German Catholicism  and Gothic Architecture?
Gero Cross: The Gero Cross or Gero Crucifix ("Gero-Kreuz" in German), of around 965–970, is the oldest large sculpture of the crucified Christ north of the Alps, and has always been displayed in Cologne Cathedral in Germany. Cologne Cathedral:  It is a renowned monument of German Catholicism and Gothic architecture and was declared a World Heritage Site in 1996.
Cologne Cathedral