Oytin Castle, located on the shores of Lake Big Oytin in the city of Oytin (Eitin), previously served as the residence of the prince-bishops of Lübeck. It is one of the significant historical and architectural monuments of the Schleswig-Holstein region in Germany. The castle is surrounded by a moat and a picturesque park, which includes Pheasant Island situated in the middle of the lake.

The history of the castle is closely linked to Russia. Here, Johanna Elisabeth, the mother of Catherine II, spent her childhood. In 1727, the castle was owned by her brother Karl August, who could have become the husband of the tsarevna Elizabeth Petrovna. The next owner was Adolf Friedrich, who, with the support of Elizabeth, ascended to the Swedish throne. It was in this castle that the future spouses Catherine II and Peter III first met in 1739.

In the 1990s, the interior of the castle was restored with funds from a foundation established by the current owners, the Oldenburg Grand Ducal House. The castle features paintings by Tishbein and numerous gifts from the Russian Imperial Family. The stables house the Museum of Eastern Holstein.