We suspect nearly all our guests coming from out of town will travel into the Frankfurt airport, which is the closest airport to where we live. Frankfurt has the only continuous skyline in the country, which is a sharp contrast to the rebuilt historic old town close by. The city sits along the river Main which is always nice to walk along. Of course there are bigger shopping districts and walking tours as any big city, but across the bridge you'll find the perfect neighborhood for Apple Wine, which is very local to Frankfurt, you can't get it everywhere. If you haven't had it yet, it makes you happy drunk, but drink too much and you might have to go to the bathroom :) Please see our Google Maps for recs.
Fulda is a mid-size city about 20 minutes from where we live. This is where we will have our welcome drinks the evening before our wedding. The Fulda Cathedral is in the heart of old town. Steps from here will lead you to a large garden or winding cobblestone streets and tons of patio seating for eating/drinking depending on which way you walk. You can easily spend a lovely afternoon here just walking around / eating. Please see our Fulda Google Maps link for restaurant recommendations.
A possible excursion 30-minutes from Frankfurt would be taking a train or car to Rüdesheim am Rhein, a town known for winemaking, especially Riesling wines. This is a pretty popular area for travelers. We enjoyed the cable car up to the Niederwald Monument for good views and a snack, and it's also where we got engaged. You can also connect to the ferry and sip on wine as you ride along the Rhine River for castle viewing. This part of the Rhine Valley is on the UNESCO list of World Heritage Sites. The ferry is about an hour and a half ride on the river one way. It has tons of covered outdoor seating and you can also order wine. You should buy tickets in town/online before boarding. Most of the castles are privately owned. There are a few that accept visitors and serve wine, but they aren't easily accessible. From what I've read online, most castles are about a 30-minute walk from the Ferry stop, and the walking paths are a little rough, and you will get dirty.
For those who want to spend a little extra time in rural Germany, we highly recommend taking a walk/hike to this castle (different from the one we will get married in). This isn't a tourist attraction by any means; it truly is just a popular walk for locals to enjoy nature. This castle is just a 5-minute drive from our house. We often walk/run/bike here either to spend some time with nature or share a quick coffee/cake/beer date. You can access it by car, or you can choose from many walking trails either on the bike path or hiking trails which will lead you here. There is a small restaurant where you can sit inside, as well as a covered beer garden. Just a 12-minute walk on the bike trail from here is a tiny old train station converted into a little pub/beer garden right on the bike trail called Frischborn Zentral Station.