Bismarck Tower, Observation tower on the Wattkopf, Ettlingen, Germany

The Bismarck Tower is a 17-metre-high square tower of red sandstone blocks quarried near the Wattkopf, standing halfway up the western slope of that mountain east of Ettlingen. Its upper third has four three-quarter columns, and four forged fire bowls sit on the capitals. A steel spiral staircase and an outdoor platform at 12.45 metres were added in 1998–99.

In the winter semester of 1899/1900, Karlsruhe university students founded a committee to build a Bismarck column, funding it through donations, garden festivals and lectures; the city of Karlsruhe gave 1000 marks. The foundation stone was laid on 1 April 1901, and the tower was inaugurated on 21 June 1901 with a torchlight procession. Cost miscalculations left a 10,000-mark gap covered by professors, earning it the nickname "Schuldenturm".

The tower's nickname "Schuldenturm" (debt tower) comes from the 10,000 marks the Karlsruhe professors had to advance when the students miscalculated costs. Student solstice celebrations with torchlight processions on the Wattkopf predated the tower, and fires were lit in its four iron bowls on Bismarck's birthday and at the summer solstice until 1914, resumed in the Weimar Republic, and were held again from 1953 to the 1960s.

The tower stands halfway up the west slope of the Wattkopf, east of Ettlingen. Since May 1999 a steel spiral staircase inside and a steel viewing platform at 12.45 m height have made it accessible to the public. The stairway entrance on the south side was walled up after a fatal accident in the 1940s.

The tower's cost miscalculation left 10,000 marks missing at the keystone ceremony; professors advanced the sum, earning it the nickname "Schuldenturm" (debt tower). The forest plot came from forester Rudolf Widman, who had bought parcels on the Wattkopf in early 1900.