Ulrich III was the ruler in the March of Carniola from c. 1249 and Duke of Carinthia from 1256 until his death, the last ruler from the House of Sponheim. His rule had long-lasting consequences. In Carniola, he acquired the former Meranian possessions, thus becoming the first undisputed princeps terrae, provincial lord or landgrave, creating the power and legal basis of the future Duchy of Carniola. The center of his original Carniolan possessions, Ljubljana, became the new administrative center and thus the provincial capital, as well as the center of Ulrich's power. In Carinthia, which he took over after his father's death, his seal became the coat of arms of Carinthia up to today. Despite his attempts to secure the vast Babenberg inheritance through two marriages, first to Agnes of Merania, widow of the last Babenberg duke Frederick II of Austria, and then to Frederick's niece Agnes of Baden, Ulrich remained childless. After a short interregnum by his younger brother Philip of Spanheim, patriarch of Aquileia, the House of Spanheim went extinct, and all of Ulrich's possessions were inherited by his cousin Ottokar II of Bohemia.