Gerhagen is a nature reserve, located between Schoot and Engsbergen in the Belgian municipality of Tessenderlo.
The area has a surface area of 945 ha. In the west, it connects to the nature reserve Averbode forest & heath, located in the municipality of Averbode. To the east lie the Schoterse Bossen. In the south, one finds the nature reserve Groot Asdonk on the territory of Diest.
Gerhagen has a number of owners, including the municipality of Tessenderlo, the Province of Limburg, the Flemish Community (on behalf of the latter: the Agency for Nature and Forests) and a number of private individuals. More than half of the area is forested with conifers, mainly Scots pine, and the oldest existing forest dates from 1915.
The area consists of a number of sub-areas, including:
* Flemish Nature Reserve De Pinnekensweier, 32 ha, consisting of two fens. Surrounding this is a mixed forest. * Flemish Nature Reserve De Houterenberg, 210 ha, consisting of forests and heathland with drifting sands. The Houterenberg is a witness hill consisting of Diestian, and belonging to a series of such hills to which the more easterly situated Rodenberg also belongs.
* Achterheide
* Heuvelken
* Schoterheide
* Gerhees
(information source: wikipedia)