Überlingen and its surrounding have to offer what ever your heart would fancy:

parks and pleasure grounds / castles and palaces
city garden with a rare tree population and famous cacti outdoor
installation; defense towers, etc.

watersports and more
sailing, surfing, diving and swimming ; golf, riding and a lot more

bike tours
The Bodensee-Radweg Service offers information around the most 
popular cycle track of Europe.

walking tours / bus-excursions
walking tour around Lake Constance leads through Überlingen. 
Additionally you can explore the charming scenery of the outback 
on lots of substantially marked ways. You can make a lot of 
excursions per ship, by bus or by train.

Here you can find a range of links: