The Royal Castle in Warsaw was the official residence of the Polish monarchs, located in Castle Square near the historic centre and Old Town. Some of the architectural attractions nearby from different periods include St. John's Cathedral, churches, and mansions with colorful details. Auschwitz concentration camp was part of a network of Nazi camps built and operated during World War 2 in Polish areas annexed by Germany. Poland is known for these concentration camps but also has interesting cities like Krakow, Wroclaw and Warsaw that attract many tourists because of their architectural heritage reflecting Bohemian, Austrian and Prussian influences. The archaeological reserve of Zawodzie in Kalisz contains the oldest area of the city, where they found coins,