Linköping is an old university city in the heart of Östergötland, Sweden's seventh-largest and the place where SAAB builds its fighter jets. The aerospace industry gives the town a surprisingly international feel for a mid-sized Swedish city.
Linköping Cathedral is one of Sweden's finest medieval churches — a 12th-to-16th century structure with a mechanical astronomical clock and a Gothic choir carved with exceptional detail. The castle next door dates back to the same era and now houses the county museum. Most of the town's older wooden buildings have been relocated to Gamla Linköping, an open-air museum village that works as a pleasant afternoon stroll. The Swedish Air Force Museum is excellent and free — worth a visit even if military aviation is not your thing, and essential if it is.
The university campus at Vallaskogen is lively, and the surrounding Östgöta countryside is flat, green, and good for cycling.