Steingrabental - Mackenröder Wald, former nature reserve in Lower Saxony, Germany

The Steingrabental - Mackenröder Wald is a former nature reserve of about 590 hectares on the southern edge of the Harz Nature Park, southwest of Bad Sachsa on the Thuringian border. It protects a section of the South Harz gypsum karst with sinkholes, karst springs, dry valleys and earth collapses. Beech and oak-hornbeam woods dominate, with farmland and fallow land in the north.

The area was protected from 3 August 1999 under the designation NSG BR 116, covering about 590 hectares. In February 2021 it was absorbed into the newly designated Gipskarstgebiet bei Bad Sachsa nature reserve. Because the Mackenröder Wald lay directly on the inner-German border during the division, it was barely disturbed and became a refuge for wildcats and black storks.

The Branntweinseiche, an old oak beside the B243 southeast of Osterhagen, was a resting place for carters on a pass; the Nüxeier Vorspann for heavy wagons ended here. Its name comes from the drivers' custom of taking a strong sip from the brandy bottle before returning to Nüxei. The custom ended with the building of the railway.

The Karstwanderweg Südharz long-distance trail runs partly through the area, in places along the former Helmetalbahn railway embankment. The southern section carries the B 243, rerouted in the 2010s, and a green bridge over the B 243 and L 603 links the area with the former Weißensee und Steinatal reserve. Expect uneven karst ground with sinkholes and seasonal streams.

An old railway route still visible today marks the Helmetalbahn, built by concentration camp prisoners during World War II as a haunting reminder of that period embedded in the landscape. Walking these paths connects nature exploration with historical reflection in a quiet, somber way that many visitors find deeply moving.