built Radzivils first privately 1. The document discusses two Belarusian castles: Nesvizh Castle and Mir Castle. 2. Nesvizh Castle was one of the oldest castles in Belarus, built in the 1600s. After 1939 it became a resort for KGB agents. In 2005 it was recognized as a world heritage site. 3. Mir Castle was originally built in the 15th century as an example of Gothic architecture. A new owner in the 16th century made additions that gave the castle Renaissance and Baroque characteristics, including a palace.