The jewel of Schleswig is St. Peter's Cathedral, a brick Romanesque-Gothic Hallenkirche (hall church) begun in the 12th century. Its towering spire makes the rest of the Altstadt seem like so many dollhouses by comparison. Inside is the outstanding 16th-century Bordesholm Altarpiece, a powerful work carved in oak by Hans Bruggeman for the convent at Bordesholm. Its elaborately carved Gothic panels contain nearly 400 figures. The cathedral and cloisters also possess art treasures, including the Blue Madonna by J. Ovens and 13th-century frescoes.