The Waldniel-Hostert was built by the Franciscan order in 1913 in Schwalmtal, Germany as a hospital-school-church complex that sheltered around 600 disabled and learning impaired people.
During the rise of the Nazi regime, the Franciscans were expelled and the function of the institution changed dramatically. At first, its adult inmates were sent for mandatory sterilization – a common fate for those who were considered by Hitler’s followers to be unwanted sectors of society, including alcoholics, schizophrenics, and people with “congenital weaknesses.” After the "euthanasia decree" of 1939, the adult inmates were sent to gas chambers.
That same decree stated that all babies born with "incurable" disabilities should also be euthanized, and the Waldniel-Hostert also became a killing center for mentally handicapped children.
It's thought that at least 97 children died at Waldniel-Hostert, most of them were killed using a large dose of sleeping medication administered one after the other in a long row. The process was slow and agonizing, taking up to eight days to finally kill some of the children. They would also develop dyspnoea, and their breath would rattle as mucous discharged from their mouths and noses.
After the end of World War II, the facility was returned to the Franciscans, who in turn sold the property to the federal government, and large sections of the building were used by the British Army as a military hospital, and then as a school beginning in 1963.
The entire complex has been empty and for sale since 1991, and people who visit the building insist that they can sometimes hear the sound of children screaming and crying in the empty corridors.