Enzo wrote:CN tower was my guess, but apparently not.
It's all a matter of definitions.
The source I used (Wikipedia) cites their source:
The Council on Tall Buildings and Urban Habitat, an organization that certifies buildings as the "World’s Tallest", recognizes a building only if at least fifty percent of its height is made up of floor plates containing habitable floor area. Structures that do not meet this criterion, such as the CN Tower, are defined as "towers".
We could relax this definition to include any structure, and then, at 553 metres, the
CN Tower in Toronto would indeed be the winner (tallest outside of the US and Asia). Until recently, the CN Tower was the tallest free-standing structure in the world, now surpassed by the
Burj Khalifa in Dubai (828 metres). Several more are planned, although these may all be in Asia and the US, leaving the CN Tower as the correct answer to my question under this definition.
Note that there are quite a few structures (other than the Burj Khalifa, they are all radio masts supported by guy wires) taller than the CN Tower.
All of them at this time are in Asia or the US, so even if we drop "self-supporting" from the requirement, the CN Tower still wins.
The only way the CN Tower does not win is if we exclude it as a "building", because it doesn't meet the definition cited above. In that case, there are three possibly winners, depending on how you measure a building's height. At 328 metres, the tallest by architectural detail is the
Sky Tower in Auckland, New Zealand. (This is the one I had in mind when I asked the question.) At 302 metres, the highest roof belongs to the Moscow Tower in the
City of Capitals in Moscow. And if we use highest to pinnacle (that is, including things like antennae), then at 355 metres,
First Canadian Place in Toronto is the winner.
Since the question asks "where" the building is, rather than an identification of the building, the answer I was looking for was "Auckland". But "Toronto" (for either the CN Tower or First Canadian Place) or "Moscow" would have been reasonable answers using different definitions.
If anyone wants to continue the thread with a new trivia question, go right ahead!