In the 19th and early 20th centuries, Sopot, then part of the Prussian partition of Poland, became a playground for Europe’s ruling classes. Kaiser Wilhelm II had a summer home here and a separate villa for his guests. Sopot in Poland became part of the Free City of Gdansk under the Treaty of Versailles and the Grand Hotel formed part of a huge casino and spa complex as Sopot enjoyed a golden age between the wars.