The first of the killing centers, Chełmno, located 30 miles northwest of Łódź operated from December 1941 until the spring of 1943. It was reopened briefly in the summer of 1944 to assist in the liquidation of the Łódź ghetto. In its first phase most arrivals were held in large house, or palace, known as the Schlosslager, where there were suffocated in mobile gas vans. Bodies were buried in mass graves several miles away in a forested area, known as the Waldlager, or forest camp. Between 152,000 and 300,000 were murdered here, including hundreds, and perhaps thousands of Roma.
There is a tiny museum and few modest markers near the site of the Schlosslager, which was razed by the Nazis in 1943. Another small museum is located at the Waldlager, where there are also many memorial structures. The main monument is comprised of a massive, irregularly shaped concrete slab—with a bas-relief on one side and text on the other—set on five squat pyramidal standards. Many of the smaller memorials at the site were erected in memory of victims by the communities where they lived.