The 553 m high television tower is the landmark of the Canadian city Toronto. The CN Tower received its abbreviation from the Canadian National Railways, the Canadian railway company which, together with other societies, had the tower erected. The start of construction work was in 1973. Three years later the CN Tower was opened to the public. Since the opening of the tower renovations have been carried out repeatedly, for example, the insertion of a huge glass floor. The tower also includes a revolving restaurant. The Canadian National Tower is currently the third highest television tower in the world.