Johnny Au
Superstar
The Seneca One Tower would be barely visible from the top of the CN Tower, though the CN Tower is more visible from the top of the Seneca One Tower.I believe you can pick up Niagara Falls on a clear day too.
I believe I remember seeing somewhere that Buffalos tallest building should theoretically be*just* visible on the horizon as well from high up, but it’s so far away you need a really clear day to see it. You need curvature of the earth calculations to figure that one out though.
Both Pinnacle One Yonge and Seneca One Tower could be visible from each other.