Toruń and the Toruń County from September 1939, were initially held in the pre-war prison, and after its overcrowding, from October 1939, the Germans imprisoned Poles in Fort VII of the Toruń Fortress. Only on 17–19 October 1939, the German police and Selbstschutz arrested 1,200 Poles in Toruń and the county. In early November 1939, the Germans carried out further mass arrests of Polish teachers, farmers and priests in Toruń and the county, who were then imprisoned in Fort VII. Imprisoned Poles were then either deported to concentration camps or murdered on the site. Large massacres of over 1,100 Poles from the city and region, including teachers, school principals, local officials, restaurateurs, shop owners, merchants, farmers, railwaymen, policemen, craftsmen, students, priests, workers, doctors, were carried out in the present-day district of Barbarka. Six mass graves were discovered after the war, in five of which the bodies of the victims were burnt, as the Germans tried to cover up the crime. Local teachers were also among Polish teachers murdered in the Sachsenhausen-Oranienburg, Mauthausen and Dachau concentration camps. Despite such circumstances, the Polish resistance movement was active in the city, and Toruń was the seat of one of the six main commands of the Union of Armed Struggle in occupied Poland (alongside Warsaw, Kraków, Poznań, Białystok and Lwów). During the occupation, Germany established and operated the Stalag XX-A prisoner-of-war camp in the city with multiple forced labour subcamps in the region, in which Polish, British, French, Australian and Soviet POWs were held. From 1940 to 1943, in the northern part of the city there was a German transit camp Umsiedlungslager Thorn for Poles expelled from Toruń and the surrounding area, which became infamous for inhuman sanitary conditions. Over 12,000 Poles passed through the camp, and around 1,000 died there, including about 400 children. From 1941 to 1945, a German forced labour camp was located in the city. In the spring of 1942, the Germans murdered 30 Polish scouts aged 13–16 in Fort VII. While the city's population suffered many atrocities, as described, there were no battles or bombings that damaged its buildings. Thus, the city avoided damage during both World Wars, due to which it retained its historic architecture ranging from Gothic through Renaissance and Baroque to the 19th and 20th century styles. Sights Listed on the UNESCO list of World Heritage Sites since 1997, Toruń has many monuments of architecture dating