My tip is definitely a trip to the Ahr Valley in your leisure time. It is a paradise for hikers, wine lovers and connoisseurs and pretty easy to access by public transport.
Travel by train to Walporzheim and then farther on by bus.
You can start the red wine trail from Bad Bodendorf and hich goes on to Altenahr. You will find the winery Försterhof where I love to sit with a glass of wine and sample the delicious food, cakes and pastries. Another favourite of mine is the restaurant at the ruins of the Marienthal Abbey just before you reach Dernau where they serve fantastic tarte flambée.
Apart from the spectacular scenery of vineyrds and valley, there is so much to see and do along the way. For example, the former Government Bunker, which is now a museum and is open to the public with interesting guided tours(https://www.regbu.de/index.html.).
An outing to the old town of Ahrweiler is definitely worthwhile and the stores are also open on Sundays and holidays. Sitting in the market square enjoying a glass of wine or an ice cream and watching the people, both locals and tourists, or just enjoying the great atmosphere is always a lot of fun for me and a great way to spend a sunny afternoon. For those interested in archeology, the town is also home to an old Roman villa, with a vast display of ancient Roman artifacts (https://www.ahrtal.de/roemervilla).
If you enjoy fine dining, you must try the gourmet Hotel Sanct Peter in Walporzheim where there will be something to suit your taste (https://www.sanct-peter.de/.).
I recommend the other bank of the Ahr River when the temperature is over 25° Celsius and it is too hot to walk through the vineyards. There is the Ahrsteig trail from Blankenheim to Sinzig and I have already ran 8 different stretches of it, but there are so many more walking routes through the shady woods. The Krausberg is a historical landmark overlooking the beautiful village of Dernau. If the flag on top of the tower is flying, this means catering is available in the cabin with food and beverages are served. There is even a playground there for the kids. A climbing center on the Neuenahrer Berg in Bad Neunahr has different levels, for both beginners and experienced climbers (https://wald-abenteuer.de/park/bad-neuenahr/). The zipline at 450 metres is one of the longest in Germany (450m) and there are over 80 climbing elements, various jumps and an Xtreme course. There is also a course for for children over 105 cm tall with the recommended minimum age of 4 years.
Starting at the end of August and extending until October, wine festivals in which the windegrowers take part in processions are in every village and in the pre-Christmas period each village has its own Christmas market. All important events can be found here: https://www.ahrtal.de/events.
I hope to see you there sometime,
Karina