We have a 5 hour stopover in Frankfurt. Is there anything to see, close enough to the airport?
You don't have to stay close to the airport. Frankfurt airport has easy and frequent connection to the city centre by public transit. And there's enough to see around the "Roemer" to keep you busy. Jo will probably have some good suggestions for you too ;-)
Here's a good starting point:
Is your stopover 5 hours between connecting flights, or a train, or 5 hours to sightsee? That makes a big difference. There is nothing to see around the airport, except forests.
The S-8 and S-9 subway will take you to the Main train station - Hauptbahnhof in 11 min. or to the Hauptwache stop in 15 min. Buy a group ticket (gruppenkarte) for 14 euro and this will get up to 5 people into town and back again and allow you to ride the trams, etc, in the city too. The S-bahn runs every 20 min.
When you get out at the Hauptwache, you are on the Zeil which is the large shopping street. You will be right in front of a large dept. store called the Kaufhof. Around the back of this is the Thurn & Taxis palace reconstruction & down the street is the Eschenheimer Turm, an original guard tower built in 1425. Walk down to the Roemer which is city hall & the town square. Alt Nikolai is the red & white church built in 1270. The river is right past this. The church on the river bank with the 2 funny towers is St.Leonhards, built in 1219. Go in there to see the "hanging vault" a 1 of a kind masonry feat, along with some beautiful star vaulting, 1400's frescos & romanesque portals from 1220. Across the street is the Archeology museum, it is attached to the city archives. The archives used to be a cloister and in there are the newly restored frescos from 1513, 150 meters worth. It is free but closed on Sat. & Sun. A visit to the Kaiserdom is also nice, or a walk down to the Holocaust Memorial Wall that surrounds the Medieval Jewish Cemetary. This wall has almost 12,000 names of Frankfurts Jewish citizens that were killed by the nazis.
You could also choose to walk thru the Klein Markt Halle, or go to the top of the Main Tower.
Leave yourself enough time to get back to the airport. You can get the S-bahn at the Hauptwache or the Konstablerwache. You can also take the tram #11 back to the Hauptbahnhof if you like. The train station is gorgeous.