At 841.9 metres, the Kahler Asten is the highest summit lying entirely within North Rhine-Westphalia. On top stands the Astenturm, a stone lookout tower that opened in 1895 and was restored after heavy damage in 1945. On a clear day the platform gives you a view of the wooded ridges of the Sauerland in every direction.

Inside the tower you will find a restaurant, a weather station where measurements have been taken since 1918, and a small nature exhibition about the heathland and winter sports on the mountain.

Around the summit lies the Hochheide, an open heathland of heather and dwarf shrubs that has been a protected nature reserve since 1965. By staying on the paths, you help protect this fragile area. Just below the summit is the source of the Lenne, the highest spring in north-west Germany, and well-known hiking trails such as the Rothaarsteig cross the mountain.

The weather up here is often different from the valley. On average it is a few degrees cooler, fog is common and in winter there is often snow. So bring a warm jumper or jacket.