Stroll around the old city and enjoy the medieval atmosphere in combination with the spirit of an university town. Visit the Elisabeth-Church, Germany's oldest gothic church, and the old castle at top of the "Oberstadt". Also worth seeing are the old university building, the city hall, and Weidenhausen the old part of the town on the other side of the river Lahn.
Take a romantic pedal boat trip on the river Lahn, which starts from the bridge opposite to the old university building. Take a hike up to the Spiegelslustturm and enjoy a wonderful view over Marburg at night. There is an exhibition on the culture and history of Hesse in the old castle and also guided tours through the "Kasematten", the cellars of the castle. Consult the tourist information office (http://www.marburg.de/det...) for details.
There is the aquamar, a relatively new swimming pool with a spa area.
Take a train in the direction of Kassel to Kirchhain, a lovely small German town with interesting large markets like the New Years Market or the Martins market.
You can also take a trip to the Amoeneburg, an old fortress 15 km east of Marburg, or to castle Rauischholzhausen, a traditional castle with a nice park.
You can also go for longer hikes in the surrounding hills and the picturesque forests.
If you are looking for culture, art and a special place to enjoy a glass of wine, visit the Kulturzentrum Waggonhalle, rigth behind the train station. Placed in the historic Waggonhalls, you will find art exhibitions, theater, concerts, flea markets, cabaret and much more. The Rotkehlchen Cafe/Restaurant serves great affordable food, tasty cakes, and offers outside seating. (http://www.waggonhalle.de/)