As mentioned by CityLab's Mark Byrnes, Canada apparently had quite the thirst for observation towers in the 1970s with impossibly tall structures popping up across the country from British Columbia to Quebec and several spots in between.
None of these towers, however, managed to reach the same dizzying heights as Toronto's CN Tower, a 1,815-foot telecommunications hub-cum-tourist hotspot that enjoyed a commendable run (34 years!) as the world's tallest freestanding structure until the Canton Tower (a fellow TV/observation tower) and the Burj Khalifa (a skyscraper) both came along in 2009. To date, it remains the tallest structure in the Western Hemisphere.
Deemed as one of the Seven Wonders of the Modern World, the CN Tower continually unveils new features to keep 'em coming back for more: the trendsetting — and mildly terrifying — Glass Floor area (1994); the world's highest wine cellar located within the renowned, rotating 360 Restaurant (1997); North America's first — gulp! — glass floor paneled elevators (1998); a spectacular, energy-saving LED exterior lighting scheme (2007); and, finally, a hands-free walk around the — double gulp! — five-foot-wide exterior perimeter of the tower's main observation pod (2011).
And although it costs a bit more, no visit to the CN Tower is complete without ascending to the SkyPod, an observation area just below the tower's antenna from which, on a clear day, you can gaze out across Lake Ontario all the way to Rochester, New York.