The Chateau Fontenac is a manor house in the area of Nouvion. On the premises of the Chateau there is also a vineyard that Monsieur Alfonse is responsible for. The series never made clear the family who owned it.
In the past, before the war, Edith worked as a maid and because of this knows the secret passages in the house. Hans Geering has also previously worked at the Chateau, presumably for General Von Klinkerhoffen.
During the series Von Klinkerhoffen is using this site as his private quarters. At one time Von Klinkerhoffen announces the Chateau will be the operational center for German military operations in the area. It is also once revealed that Lt. Gruber has his private quarters here, after he is acquired by Klinkerhoffen to be his ADC.