Wetzlar is a city in the state of Hesse, Germany. It is the twelfth largest city in Hesse with currently 55,371 inhabitants at the beginning of 2019. As an important cultural, industrial and commercial center, the university town is one of the ten regional centers in the state of Hesse. A former free imperial city, it gained much of its fame as the seat of the Imperial Supreme Court (Reichskammergericht) of the Holy Roman Empire. Located 51 kilometers north of Frankfurt, at 8° 30′ E, 50° 34′ N, Wetzlar straddles the river Lahn and is on the German Timber-Frame Road, which passes mile upon mile of half-timbered houses. Historically, the city has acted as the hub of the Lahn-Dill-Kreis on the north edge of the Taunus. Tourists know the city for its ancient town and its medieval Catholic/Protestant shared cathedral of St. Mary. Notable architectural features include the Eisenmarkt and the steep gradients and tightly packed street layout of a medieval town. The building of the sandstone cathedral commenced in the 12th century in Romanesque style. In the later Middle Ages the construction continued under a master plan in Gothic style. The church was never finished—one steeple still remains uncompleted. The cathedral suffered heavy damage in the Second World War from aerial bombing, but restoration took place in the 1950s. On the outskirts of town along the river stand the ruins of several stone towers.

Hesse or Hessia, officially the State of Hesse, is a state in Germany. Its capital city is Wiesbaden, and the largest urban area is Frankfurt, which is also the country's principal financial centre. Two other major historic cities are Darmstadt and Kassel. With an area of 21,114.73 square kilometers and a population of over six million, it ranks seventh and fifth, respectively, among the sixteen German states. Frankfurt Rhine-Main, Germany's second-largest metropolitan area, is mainly located in Hesse.