Ketrzyn - Poland town located in Warmia-Mazury. Its modern name of the city received only in 1946 in honor of the Polish historian Wojciech Kentshinskogo. Before World War II German name Ketrzyn wore Rustenberg.

In the fourteenth century on the territory of modern Kętrzyn it was built a defensive fortress of the Teutonic Order, which had in 1311 attempted to lay siege to the Lithuanian prince. In the thirties of the fourteenth century began the construction of wooden gates, which was later replaced by a stone castle. Gradually the settlement was surrounded by 13 defensive towers, two gates were built. Construction of the castle contributed to the rapid economic development of Kętrzyn, which received city rights 11 November 1357.

Ketrzyn and the surrounding area took an active part in the hostilities of the First and Second World Wars. During the Second World War in the woods east of Kętrzyn was built headquarters of Hitler's "Wolf's Lair". The bombing of 1942, the fighting in 1945 led to serious destruction of the city. The castle and old town were burned by soldiers of the Red Army. Number damage reached 40%.

In 1946 the town was incorporated into the newly formed province of Olsztyn. German-speaking population of the city was deported to Germany. The city's name was changed to May 7, 1946.

Despite severe damage in Ketrzyn, numerous monuments and other attractions that attract tourists today. The Gothic Teutonic castle is a museum and the city library, various cultural events and music concerts. Among the religious monuments most valuable is perhaps the Gothic Basilica of St. Jerzy Lutheran Church and St. John.