I went up the CN Tower last month on the first leg of my holiday. The CN Tower and area surrounding were packed with police as they arrived a week prior to the G20 summit to run security checks.
I have to say, this building was a nightmare to take photos from ... the first observation deck has a lot of internal lights that reflect in the glass windows, ruining evening / night shots of the city.
This picture is taken from the skyport, 447m above the city. Spectacular views but as we arrived they'd started to illuminate the building (hence the blue tinge) - they also have restricted views through these conservatory style windows :(
In person the views are great but photography wise - nightmare!
I left my tripod downstairs (not sure if they'd permit them anyway) and took my trusty Joby SLR Zoom gorillapod with me. Fairly heavy crop on this to cut out the bulk of the window frame!
Why f/6.3? The exterior lights were running on a sequence and I was trying to squeeze my exposure inside the time they turned the lights out (~5 secs). I should have dialed in more negative exposure but at the time I opened the aperture up slightly (from f/8) to reduce the exposure time.