At the heart of the Molenheide area lies a second, unnamed fen that appears much more natural than its edges suggest. This fen lies deeper in the forest and heathland mosaic and is completely surrounded by mixed coniferous and deciduous forest that gradually transitions into open heathland. The water body is small, shallow, and highly dependent on rainwater and the local groundwater level. As a result, the water level can fluctuate significantly in wet and dry seasons, creating a dynamic peripheral zone with low peat formation, moor grass, and moist heathland vegetation.
Due to its protected location, further from the edges and paths, the fen is a peaceful place where dragonflies, green frogs, and birds such as the wren and blackcap like to forage. Mosses and specific fen plants thrive there precisely because there is little human disturbance. The fen is part of the natural diversity that characterizes the Molenheide: open water amidst dense forest, interspersed with heathlands and grassy areas where highland cattle ensure that the landscape remains open.