Twenty thousand treasures from the house of Hanover, the royal family headed by the controversial Prince Ernst August, goes under the hammer this week in one of the last auctions of its kind in Europe. "It is the last auction of a royal family in Germany, perhaps even on the continent," said Christoph Douglas, the cultural advisor to the prince and the former head of the Sotheby's auction house in Germany. It has sent more than 100 experts to Marienburg, a fairytale neo-gothic castle in a forest south of Hanover, to put the finishing touches to the dizzying display before the buyers come on Wednesday for the start of 10 days of sales. Prince Ernst, the third husband of Princess Caroline of Monaco, has given his two sons, Ernst August Jr. and Christian, permission to sell the family silver to raise money for a fund to maintain the 130-room property, his spokesman Mauritz von Reden said. The two young aristocrats, who are both studying in the United States, plan to retain a few pieces of art and open the castle to the paying public. The objects on sale are expected to fetch at least 12 million euros ($14.3 million).