Csörgő (Rattling) brook is the most significant brooks of the High Mátra mountains that originates from Mátraszentistván. It was named after the sound of the rock and pebbles when flood occurs. In 2000 on the more than 300 hectare-area in the valley of Csörgő brook a forest reserve of special natural value was designated so that the natural development processes of the forest could be studied. In the picturesque valley the green □ symbol guides us that passes a reconstructed glass plant (üveghuta) that relates to an old trade. The valley is accessible from the direction of Mátraszentistván, Mátraszentimre, Mátrakeresztes or Ágasvár tourist house.