This is Mainz Cathedral, its academic name is St. Mardin's Cathedral, one of the largest and most gorgeous cathedrals in Germany, and the cathedral of the Catholic Diocese of Mainz. In fact, the interior decoration of the church has been interpreted as a Catholic church. I found several places in the market square next to the church, and I couldn't take the whole picture, but I could only walk to the far side of an alley behind the church, and I barely included several towers of the church together (the first photo).