Astenturm, Stone observation tower in Winterberg, Germany

The Astenturm is an observation tower on the summit of the Kahler Asten, a 841.9 m mountain near Winterberg. Its viewing platform stands at 862 m, making it the highest point in North Rhine-Westphalia reachable by asphalt road. The tower also houses a weather station and an attached hotel-restaurant.

The Astenturm stands on the Kahle Asten, which at 841.9 m is the third-highest peak of the Rothaargebirge and the highest summit lying entirely within North Rhine-Westphalia. A permanently staffed weather station of the Deutscher Wetterdienst operated inside the tower until 2016; the last manual report was sent on 22 March 2016, after which it became an unmanned station. Its viewing platform at 862 m makes the mountain one of the most frequently named in German weather reports.

The tower draws hikers and winter sports enthusiasts who gather here to rest and enjoy the views. For many, it serves as a popular stopping point on their route through the mountains.

The summit is the highest point in North Rhine-Westphalia reachable by asphalt road, so drivers can park close to the tower. The viewing platform sits at 862 m, above the 841.9 m summit. In winter, snow cover lasts an average of 120 days a year, and the maximum snow depth has reached 239 cm, recorded on 9 March 1970.

The weather station inside the tower was staffed around the clock until 2016; the last manual report went out on 22 March 2016 at 14 UTC. Since then it has run unmanned. The tower's viewing platform sits at 862 m, higher than the 841.9 m summit itself.