Windknollen, Summit in Jena, Germany.

Windknollen is a 363-metre-high, bare hill northwest of Jena's Saale valley, underlain by shell limestone and covered mainly by subcontinental semi-dry grassland. The plateau, a 195-hectare nature reserve within the FFH area Isserstedter Holz – Mühltal – Windknollen, has short-grass vegetation resembling North American prairie and Mongolian steppe. Old trenches, embankments and overgrown landfills mark the terrain, and the Napoleonstein stands on the summit.

The hilltop was a site of the Battle of Jena and Auerstedt and is marked by the Napoleon Stone, which commemorates these events. Later, the area served as a military training ground until military use ended in 1990.

The name Windknollen refers to the windy exposure of the hilltop, which shapes the landscape. The dry grasslands and specialized plants create an unusual setting that resembles steppe environments and attracts many rare animal species.

The hilltop is accessible via several walking trails that offer good conditions throughout the year. The paths are marked with navigation aids and suit visitors of different experience levels.

The plateau's short-grass vegetation is compared in the sources to North American prairie and Mongolian steppe. Small water bodies here shelter the northern crested newt and the European tree frog, and since 2018 the 195-hectare nature reserve was offered for sale, with the NABU National Natural Heritage foundation acquiring much of it.