The Deutschordensschloss is the undisputed centrepiece of Bad Mergentheim. The castle evolved from a 12th-century medieval fortress into an elaborate Renaissance and Baroque palace complex covering some 3,000 square metres — the product of centuries of Grand Masters each adding their mark. The result is a layered building that rewards careful attention: the Renaissance courtyard is particularly fine.
The palace church, completed between 1730 and 1736, is a highlight in its own right. It was designed with input from Balthasar Neumann and François de Cuvilliés, two of the most celebrated architects of the German Baroque, and features ceiling frescoes of considerable quality. The museum inside the palace covers the history of the Teutonic Order from the Crusades through to the Napoleonic dissolution, with a collection of medieval armour, ceremonial objects, and a scale model of Bad Mergentheim as it looked around 1750.