Lake constance

Cycling around parts of the lake then take the bike onto the ferry (for example friedrichshafen to Bregenz), meersburg castle , Konstanz has a great center, etc -
Our teens pretty much like what we do tho! Bodensee is beautiful - but we have family there so we visit with an added purpose.

Maybe visiting the Zeppelin museum (https://www.zeppelin-museum.de/en) or the sunken stone age village (https://www.bodensee.eu/en/what-to-do/map-of-lake-constance/lake-dwelling-museum-unteruhldingen_poi160) would be something.

The first time I experienced Lake Constance, I was on a HS trip. We visited the Rheinfalls and the Island of Mainau. Mainau is a botanical garden, and has some incredible flowers and it is on the lake so some really great views.

As an engineer, I found the Zeppelin museum absolutely fascinating.

I love the town of Lindau. I've visited it as a day trip from the Oberallgäu multiple times and spent four nights there in 2017.

Another vote for the Zeppelin Museum. It is an outstanding museum. And although we didn't do this, there are zeppelin flights over the lake that I suspect even jaded teens would enjoy. We also thought the city of Konstanz was very pleasant and cosmopolitan if you want to build in some shopping and dining (great Lebanese and Vietnamese). Taking the ferry out of the eastern mouth of the lake into Untersee and down the Rhine River is a great ride. St. George's Abbey in Stein am Rhein may not seem like an obvious choice for teens, but the frescoes inside are full of knights, battles, damsels, castles, etc. The whole region is a mecca for outdoor activities -- hiking, swimming, canoeing, kayaking, biking, etc. Also fishing is a huge industry and you can find fishing guides and charters too. Plus, the fish served at restaurants is fantastic! If they are older teens, Lake Constance has an outstanding wine micro-climate, particularly along the north shore. A vineyard and winery tour could be fun. If they are younger teens, maybe give them some movie money and have the adults go one afternoon! ;-) Bottom line, we loved this region. I think you'll have a great time no matter what!