The Brennerštôlnian water reservoir located in the so-called Zelené valley (Grünthal) in the cadastre of the village of Hodruša-Hámre, 1.5 km north-east of the square in Banská Hodruša and 1 km southeast of Rumplovská, at an altitude of 555 m.

It is the oldest water reservoir in the Hodrušská group, built before 1584, when it is mentioned in the inventory of the assets of the Brennerštôlnian Mining Company. The width of the dam is 30 m, the height is 10 m, the volume of the water reservoir was 19,100 m³ of water. It probably lost its original meaning already in the 18th century, after repairs and completion of the Upper and Dolná Hodrušská water reservoirs. In the 1950s, it was callously devastated and abandoned. It has the largest dam, up to 30 m in the crown. It is almost dry today.