In 1924, the Curfs family started small-scale extraction of Marl, and the extraction was expanded over the years. Extraction stopped in 2009, resulting in a quarry of 40 hectares with a depth of more than 60 meters in places. An impressive hole with special nature that, due to its location surrounded by wooded slopes, grows unusual plants and attracts insects such as butterfly species that normally occur in southern regions. Merssenerbroek was agricultural land until the mid-nineties of the 20th century. After the agricultural activities ended, forests spontaneously arose. If the Geul has to drain a lot of water via the Geulke, the Meerssenerbroek may flood again. The Dellen consists largely of a high plateau with forests with some tough climbs and descents. The highest part is currently still used by defense as a military training area.