12 hours in Frankfurt-what do do?

Frankfurt on Foot Walking Tours

No lockers at the airport. Are you sure you have to pick up your luggage or are you just looking for a spot to store your carry-ons? There are luggage storage facility at the airport that charge 7 € per bag or you can come into the city and store your bags in a locker at the main station.

What kind of interests do you have? Frankfurt has a ton of sites, but help me narrow it down so I'm not typing all night. :-)

Well, are there any interesting neighborhoods, such as a historic old town? Any museums you would consider must-see (although art museums aren't really our thing)? Any historic buildings or castles that can be toured?
Thanks!

No castles in Frankfurt. If I had your dates of travel, I could send you some events. Nice, old neighborhoods in Bornheim, Sachsenhausen, and Höchst.
Recommended sites to see?

• The Römer and the Römerplatz. City Hall since 1405 and old town square.
• Book Burning Memorial, site of the Nazi book burning
• Alt Nikolai Church, Gothic church, built 1290
• House Wertheim, the inner city's only original half-timbered house left at the end of World War II,
• Eisener Steg, pedestrian bridge over the Main river, offering a great view of the skyline and the many museums lining the riverbanks. Love lock bridge
• St. Bartholomew, better known as the Kaiserdom, Imperial Cathedral chosen as the site for Coronations and Elections of the Holy Roman Emperor for centuries
• Jörge Ratgeb Wall Paintings in the Karmeliter Cloister, the largest religious wall paintings north of the Alps, painted in the early 1500's.
• Stumble Stones, or in German, Stolper Steine. Unique way of remembering many of the victims who lost their lives due to the nazi regime.
• Jewish Holocaust Memorial Wall - a very personal Memorial that the city of Frankfurt has created to honor the memory of the over 12,000 Jewish citizens of Frankfurt who were sacrificed during World War II. Anne, Margot, and Edith Frank are included on this wall of remembrance.
• Medieval Jewish Cemetery - one of the oldest and largest Jewish cemeteries in Germany (get the key from the museum)
• Jewish Ghetto Wall - Once part of the city defenses in 1180, it later became one of the walls that surrounded the Jewish ghetto.
• Klein Markt Halle - wonderful produce hall, filled with fruits, vegetables, chocolate, pastries, cheeses, breads, meats and fish, and delicacies from around the world. (not on Sundays and holidays)
• Bull and Bear and the Frankfurt Stock Exchange
• Thurn and Taxis Palace, reconstructed, but a lovely example of architecture from the 1700's.
• Eschenheimer Turm, original guard tower, once part of the city defensive walls, built in 1428
• Alte Oper, one of the classic opera houses in Europe, once known as the most beautiful ruin in Germany
• Goethe House, where Goethe was born
• Paulskirche, the location of the first parliament of Germany in 1848.

Thank you so much! This will help plan our day.