CN Tower is the symbol of Toronto and is North America's tallest free standing structure!
It now ranks as the 4th tallest such structure, but is probably the most well-recognized of the bunch.
http://en.wikipedia.org/wiki/CN_Tower
http://en.wikipedia.org/wiki/CN_Tower
Going up to the top is a must. They are trying to work on an Edgewalk where you can walk outside around the circumference of the observation deck. No thanks for me.