Wikipedia
Felsennest
At the start of the Western European campaign of 1940, the Felsennest ("Rocky Eyrie" in English) was the codename for one of Hitler's Führer Headquarters near Bad Münstereifel, Germany. It was much more cramped than Adolf Hitler's other field bunkers, having only four rooms. Hitler was at the Felsennest in the autumn of 1939, because there were plans to invade France and the Low Countries. He was there again on May 10, 1940 when the invasion took place.