Dicke Tannen is a protected landscape, around 4.2 hectares (10 acres) in area, near the Harz village of Hohegeiß, which lies in the borough of Braunlage.
The trees, which are up to 350 years old and known colloquially as Rottannen ("Red Firs") were first mentioned in the 18th century in forestry documents.
They owe their survival, firstly, to their location on the steep, wind-sheltered slopes of the narrow Wolfsbach valley; secondly, the fact that they were almost too difficult to fell with the axes and saws of the time on account of their huge size and the transportation of their timber would have proven almost impossible.
As a result the area has not been used for forestry for over 200 years and thus gives the impression of almost being a virgin forest.
Apart from those reaching their natural age limit, changing environmental conditions may also have affected them.