The Frankenteich (also called the Sägemüllerteich) is an old reservoir in the Harz Mountains of central Germany.
It was constructed in 1716 under the direction of mining director (Bergwerksdirektor), Christian Zacharias Koch, for the mining industry and is the largest pond in the Lower Harz.
A mining ditch runs past the foot of the dam from the Kiliansteich which, like the Frankenteich, belongs to the heritage area designated as the Lower Harz Pond and Ditch System.
The dam, which is made of argillaceous and quartzitic shale, is sealed with an internal core of grass sods.
During the overhaul, a section was cut in the bottom outlet in the centre of the embankment and then replaced with a new seal of clay and silt and new pipework.