Karl Anton built the castle into a meeting point for the nobility of Europe. Portions of the castle were rebuilt and decorated to make Schloss Sigmaringen into a destination of the rich and powerful. In 1855 the walls of the upper story were removed to create the Old German Hall (German: "Altdeutschen Saal"). In 1864 he modified the arches above the southern curtain wall to form the Weapons Room (German: "Waffenhalle"). From 1862 until 1867 he built the new Art Gallery (German: "Kunsthalle"), which is today a museum. As a member of the German high nobility, Karl Anton needed a centerpiece of his elegant castle. To create this, in 1872 he had the Parisian architect Lambert rebuild the dining hall into the French Hall (German: Französische Saal). In 1877 he expanded the central keep, removed the old roof and topped the keep with a new pointed roof. In the following year, the Ancestors' Hall (German: "Ahnensaal") was rebuilt.