A maar volcano created this wide basin with a diameter of around 1.5 kilometers. The original maar lake in the funnel silted up and was dammed in Roman times to create a pond with a rich fish population. When the water was finally drained in 1838, the western part of the pond was used as farmland.
Today, this is the meadowland we are standing on, while the eastern part is occupied by a moorland area. Peat was cut there until the 1950s. Today, the fen with its copses of eared willow and alder tree is a designated nature reserve.
