Frederick had famous buildings constructed in his capital, Berlin, most of which still exist today, such as the Berlin State Opera, the Royal Library (today the State Library Berlin), St. Hedwig's Cathedral, and Prince Henry's Palace (now the site of Humboldt University). However, the king preferred spending his time in his summer residence Potsdam, where he built the palace of Sanssouci, the most important work of Northern German rococo. Sanssouci, which translates from French as "carefree" or "without worry", was a refuge for Frederick. "Frederician Rococo" developed under Georg Wenzeslaus von Knobelsdorff.