During my research I saw an old map view of the city of Frankfurt am Main that was engraved by Matthaus Merian, the father of Maria Sybilla Merian. On this map were the tiny figures of a (dark) crucifix with a (gold) rooster above it. This was placed to indicate the middle of the bridge where the river was deepest. The larger boats needed to stay in the deep section going under the bridge; if they chose one of the other arches they could easily have ended up stuck in shallow waters.
There is a legend told of this golden rooster, called by the old name of Briggegickel. It seems that each time a bridge was built over the river connecting Frankfurt with Sachsenhausen on the other side, before long it would be washed away by a flood. The city decided this time the bridge should be of stone. They hired an expert stonemason to do the job, then told him it had to be built in two days. He rounded up a crew and they went to work. He realized that it would not be done in time and was very worried.
A stranger appeared to the stonemason and said that he could get the bridge finished in time, and for payment he required only the soul of the first two-legged being to cross the new bridge. The worried stonemason, seeing hope for the first time, quickly agreed.
Early the next morning the stonemason awoke with a heavy heart. His shoulders slumped as he went to join the town council for the opening of the new bridge. He realized that, as the stonemason hired to build this bridge, HE would be the first to cross it. And he had agreed to exchange his soul for the completion of the bridge. He had made an agreement with the devil. Almost at the bridge, his footsteps slowed. He looked around and saw a rooster strutting nearby. He grabbed the rooster and ran to the edge of the bridge.
The devil was waiting at the other end. The stonemason tossed the rooster onto the bridge. The squawking rooster ran the length of the bridge to the other side. “There’s your two-legged being!” shouted the stonemason. And he leaped for joy because he had just beat the devil.
The stonemason told the city council what had happened; the story spread. A sculptured golden rooster was added to the crucifix on the bridge to commemorate how the stonemason had outwitted the devil.
The golden rooster and the dark crucifix can be seen today in the Historical Museum of Frankfurt.