In July 1944, the 'Cuckoo' project underground synthetic oil plant (800,000 m2) was being "carved out of the Himmelsburg" North of the Mittelwerk, but the plant was unfinished at the end of WWII.
U lipnju 1944., projekt 'Cuckoo' - podzemno postrojenje za proizvodnju sintetičkog ulja (800,000 m2) je izgrađeno u Himmelsburgu, sjeverno od Mittelwerka, ali je postrojenje ostalo nedovršeno sve do kraja Drugog svjetskog rata.