This is Sweden's second largest lake and the fifth largest in Europe, measuring some 129km (80 miles) from north to south. The average depth of the lake is 38m (125 ft.) and the deepest measured depth, south of Visingsö, is 127m (417 ft.).
The lake is known for its sudden storms. At times, we've sailed on it and the waters were placid. But on one occasion a sudden storm arose, whipping the water into dangerously choppy waves and almost overturning our boat. That said, the inland lake, which once was a sea bay, is always great for angling. There are 28 different fish species remaining in its freshwater. Some of these species have lived here since the Ice Age, including the famous Vättern alpine char. There is also an array of pike, perch, and pikeperch, along with grayling, salmon, and brown trout.
When it comes to swimming, Lake Vättern has both a good and a bad reputation. On the one hand, not many inland lakes can offer such long, Riviera-like beaches with water that is virtually drinkable; on the other hand, its temperature varies greatly because of its depth -- one day it's suitable for swimming, and the next day it's icy cold.
Jönköping (350km/217 miles southwest of Stockholm or 150km/93 miles northeast of Gothenburg) can serve as your gateway to Lake Vättern, especially if you're driving north from Småland. However, even more charming places can be found along the lake, especially the towns of Gränna and Vadstena, as well as Motala.
Following the eastern shore, E4 offers the most scenic route, providing panoramic vistas across the lake.