Even if you only have a few minutes to spend - Nathan Phillips Square is a pretty awesome spot to walk through while visiting Toronto.
The square itself is lovely - open, water fountain feature right in the middle, plenty of benches situated all around with views of all sorts of lovely architecture - the old City Hall in its Romanesque glory, and the 'new city hall' with its glass and concrete and modern style. I love the stark contrast of the neighborhood.
The best part of this square though is without a doubt the giant TORONTO letters - which create the ultimate and best touristy moment. Hubs and I spent way too much time posing in front of the letters but we came home w/ a couple really great photos.
Bonus - the giant letters light up at night! And if you sit there and watch it for a bit it ends up being a light show - changing between red/white/blue to pink/green/yellow. I can't decide if I like the daytime or nighttime views better... if you've got the time and are close by - try and visit the square both during the day and after the sun sets. No visit it complete without a goofy photo in front of the Toronto letters!!