Chełmno extermination camp
Chełmno, or Kulmhof, was the first of Nazi Germany's extermination camps and was situated 50 km (31 mi) north of Łódź, near the village of Chełmno nad Nerem. Following the invasion of Poland in 1939, Germany annexed the area into the new territory of Reichsgau Wartheland.
Source: Wikipedia — Chełmno extermination camp (CC BY-SA 4.0)