Konrad von Horneck donated his castle to the Teutonic Knights in 1255. During the office of Eberhard von Seinsheim (1420-1443), it became the residence of the Grand Master of the order. After the castle’s destruction during the Peasant War in 1525, the Grand Master's residence was relocated to Mergentheim. In 1533, the reconstruction of Horneck as a Renaissance castle including Komturei (an administrative office of the order of the Teutonic Knights) was completed. Franz Ludwig von Pfalz-Neuburg – Grand Master (1694-1732), Prince-Bishop of Breslau and Elector of Trier – had Horneck reconstructed in the form of a baroque palace from 1724 onwards, which was carried out by the Order's master builders Franz and Johann Michael Keller. In 1805 the castle fell to Württemberg and thereafter was used as military barracks, for example, and sold several times. In 1891 Friedrich Trump established a sanatorium for natural medicine. In 1897 the sanatorium was taken over by the Schloss Hornegg GmbH and developed into a sanatorium for upper class patients, headed by senior consultant Dr. Ludwig Roemheld. After the building had been used as a military hospital during World Wars I and II, it served as a sanatorium for lung diseases from 1946-1957. From 1960 to 2015 it was the Heimathaus Siebenbürgen, a nursing home for the elderly and patients requiring care. In October 2015 it became a Transylvanian cultural centre. It is still home to the Siebenbürgen Institute and the Transylvanian Museum – the most important Transylvanian cultural institutions outside of Romania.