Here are some postcards showing early views of Frankfurt with streetcars. The first two are both from about 1910, showing the same church from different angles.
On the next one, sent in 1903, you can see the overhead wires.
The last card shows an electric tram in front of the magnificent Circus Schumann, which was destroyed by Allied bombs in World War II. According to Circopedia, the U.S. Army used what was left of the building (the facade, foyer, and restaurants right behind it) until 1958. The remains of the building were demolished in 1960.
That white object in the sky to the right of the building is a highly-stylized cloud, probably the strangest one I've seen, added by the person who tinted the card. This tinting process was also used to obscure unsightly things like overhead streetcar wires.
I love it when people write dates and document other happenings on the back of cards. If we had been around 100 years ago, we too could have celebrated Otto's birthday at Circus Schumann.