On 13. July 1817 Princess Charlotte, oldest daughter of King Friedrich Wilhelm III and Queen Luise, married Nikolaus (who later became Tsar Nikolaus). In the summer of 1818 Friedrich visited his daughter in Petersburg and was entertained in a Russian style blockhaus. As a suprise for his daughter & her husband, he asked a captain of the pioneers batallion to build a block house to plans supplied from Petersburg.

Now it's a place for coffee and cake (or a meal), with a great view out over the water.