House of Gorizia
The castle was probably erected in the 12th century, as one "Witemarus de Sumereke" was already mentioned in an 1187 deed issued at Neustift Abbey in Tyrol. The Lords of Sommeregg then served as "ministeriales" of Count Otto II of Ortenburg, who ruled over extended estates in Upper Carinthia, rivalling with the House of Gorizia and the Salzburg archbishops. On 29 May 1275 the marriage of Otto's granddaughter, Euphemia of Ortenburg-Hardegg, with Count Albert I of Gorizia was arranged here.