Blauer Steinbruch, Nature reserve in Ehingen, Germany.

Blauer Steinbruch is a protected nature reserve of 5.2 hectares centered around a former quarry with a lake covering about 1 hectare. The landscape shows clear signs of its mining past, with steep banks and visible layers of rock and earth.

From 1890 to 1925, limestone was extracted from the quarry to supply the Ehingen cement factory, one of the largest cement producers in the Kingdom of Württemberg at that time. After extraction stopped, the quarry filled with water and gradually transformed into a nature reserve.

The name Blauer Steinbruch refers to the blue colour of the water, caused by the cement marl that was quarried here and the water's high clay content. The quarry was worked from 1890 to 1925 by the Ehingen cement factory, then the largest of its kind in the Kingdom of Württemberg.

The nature reserve is accessible through several hiking trails of varying lengths and difficulty that connect to different viewing spots. The paths are easiest to walk during dry weather, as they can become slippery after rain or during wet seasons.

The orchid species recorded here are the marsh helleborine, the two-leaved forest hyacinth, the common twayblade and the musk orchid on the semi-dry grassland, plus the military orchid on the sunny slopes. The lake also holds eight amphibian species, and little grebes and tufted ducks breed on it.