Anneessens Tower, Fortified tower on Boulevard de l'Empereur, City of Brussels, Belgium

Anneessens Tower is a stone defensive structure from Brussels' original city walls, built with thick stone walls and positioned strategically along Boulevard de l'Empereur. The structure shows the characteristic design of medieval fortifications and remains visible from street level, standing between numbers 34 and 36.

Built in the 13th century as one of the watchtowers of Brussels' first city wall, spaced about 50 metres apart between the gates, the tower lost its military role when a second, larger wall absorbed the first in the 14th century. It survived because houses were built around and over it; around 1870 the architect Jean Baes set up his studio inside. In 1957 the widening of Boulevard de l'Empereur freed it from later buildings, and it was restored several times before being listed in 1992. Tradition holds that François Anneessens was imprisoned here, but he was actually held in the nearby Steenpoort, connected to the tower by a passage.

The tower takes its name from François Anneessens, dean of the Four Crowned Martyrs guild, an association of sculptors, stone carvers, and masons. This craft guild shaped the identity of Brussels' medieval artisan communities and remains embedded in the city's cultural memory.

The tower stands along Boulevard de l'Empereur, opposite the PS headquarters, and is not open to the public, so it is seen from the street. It was freed from surrounding houses when the boulevard was widened in 1957. The darker lower level is the foundation course exposed by the North-South railway works.

The tower owes its name to François Anneessens, dean of the Four Crowned guild, though tradition is wrong: he was held in the nearby Steenpoort, which served as a prison, and a passage linked that gate to this tower. The tower itself was long swallowed by a house block; architect Jean Baes lived there around 1870 and set up his studio inside it.