The water castle ruins are the remains of the old water castle from the 12^th/13^th Century which served as a border fortress between the Margrave of Meißen and the Count of Dohna. Of its original structure today remain a tower of 12 meters height, a wall of 1.5 meters and a wall fragment of 18 meters length. The tower consists of a basement and a first floor and comprises several embrasures. The basement is covered by a dome ceiling with a still intact quadrangular hole in the middle which once allowed access to the basement.

Already in the 12th Century, the first inhabitants settled down protected by the water castle. Against some legends, there is no indication that the place has ever served robber knights. Most likely, it was meant to protect the important communication road between Freiberg and Dippoldiswalde. After the power of the Counts of Dohna had diminished in 1402, due to the destruction of their main castle in Dohna, the Ruppendorf castle lost its strategic value. It remains unknown whether after this the castle was still inhabitated or started to decay.

The castle was once surrounded by a water ditch and a pond which, apart from a small area, were transformed into meadows around 1840. An oil crush was located close by. The exact date of its disappearance is unknown. The ruins had been much bigger until 1869, however, left in a poor condition. In that year the neighboring outworks (cf. Information board 23) burned down. It was reconstructed with the help of large parts of the ruins that served as construction material without further consideration. The ongoing decay of the tower was stopped when luckily the outworks’ owner Wolf, who had owned a part of the outworks since 1888, initiated the reconstruction of parts of the tower and the mending of the brickwork.

In 1998 the facility was further restored. The ruins of the former water castle are now a protected monument. They are considered a landmark of the village and are an important part of history for its inhabitants.