Bismarck Tower, Historical observation tower in Unna, Germany.

The Bismarck Tower in Unna is a stone observation tower that offers visitors views across the surrounding region. The structure is solidly built and provides wide sight lines from the top across the flat landscape of the area.

A committee founded in Unna on 21 February 1899 commissioned the tower, built in 1899–1900 to a design by Bruno Schmitz and inaugurated on 18 October 1900. It was the first monument of its kind in Westphalia; the cost of 33,000 marks was kept low because several participants worked unpaid or cheaply. After 1918 it lost its political symbolism but remained a popular excursion destination.

Three times a year the tower hosted patriotic gatherings: on Bismarck's birthday (1 April), Sedan Day (2 September) and the founding of the Empire (18 January). After 1918 it lost its political role but stayed a popular excursion and viewing point; in the 1920s fires were still lit on Bismarck's birthday, and in the 1950s expelled Germans from the eastern territories celebrated St John's Day here with a bonfire in the fire basket.

The tower is accessible at set times, mainly on the first Sunday of each month and by appointment. Visitors should check ahead or arrange a visit to ensure access.

The tower's fire basket, where fires burned on national holidays before 1919, was removed in 1989 and replaced by a steel frame carrying a board cross that serves as a trigonometric survey point. Two information boards from the Geological Survey of North Rhine-Westphalia now let visitors read the geological past of the Sauerland, the Münsterland basin and the northeastern Ruhr area.