Mirabell Palace (Schloss Mirabell) is part of the Altstadt of Salzburg, a UNESCO World Heritage Site, and was built for the Prince-Archbishops of Salzburg in the 17th century. Today it houses the city council, with parts of the palace available to visit, and the beautiful gardens are a huge draw, especially in summer. You might even recognize the fountain and steps from the movie The Sound of Music!