The Kütfelsen, an impressive watch glass-shaped hill, was formed by the deposits of the carbonated brine spring "Unitas". This spring formed the rock, which is over three meters high, on the level of the Hederkiese. The oldest layers of the sintered rock are estimated to be over 15,000 years old. In the immediate vicinity is the well house, which was built in 1554 and is a listed building. It was carefully restored in 1980/81 with the support of the Westfalen Office for the Preservation of Monuments. The well house, built directly above the brine spring, provides the "Unitas Quelle" with the necessary protection.