If you are going to Geneva for a weekend you could hire a car at Geneva airport and explore the towns and countryside lining the northern side of Lake Geneva which contain a pleasing mix of major sights such as Chateau de Chillon, one of the best preserved castles in Europe and quiet rural villages and lakeside towns.
The region can be explored in a day or two by car. The narrow lakeside plain quickly gives rise to the foothills of the Bura river. The South facing slopes are covered by vineyards and there are stunning views of Mont Blanc and the Alps on the other side of the Lake.
If you have more time, drive your car hire to Lausanne, a city built on hills and visit its extraordinary cathedral, a great example of Gothic architecture.