I had such a hard time picking one photo - Toronto is so large and beautiful that simply one photo can not represent it!
However...
I'm not sure that its the single most beautiful picture of Toronto (it doesn't even include the financial core), but I love this photo lets you almost feel like your there. A warm summer night with on the lake, with the bright and colourful city in the background. Full of activity!
There are so many other photos that are probably more beautiful and deserve to be posted here (am I allowed to link them in this thread?
). However, I really like this photo.