The Duchy of Brunswick-Lüneburg was a historical territory in northern Germany, established in the late Middle Ages. It was part of the larger Holy Roman Empire and consisted of several regions, including the cities of Brunswick and Lüneburg. The duchy was known for its economic prosperity, particularly due to its salt mines and trade routes. Throughout its history, the duchy was ruled by various noble families, including the House of Welf. In the 16th century, it became a significant center for the Reformation in Germany. The duchy eventually fragmented into smaller principalities, contributing to the complex political landscape of the region.