For "Toronto ON" it's the intersection of University and Dundas, just north of City Hall. The intersection looks like this:
https://www.google.com/maps/@43.6548154,..._ep=EgoyMDI2MDYwMy4xIKXMDSoASAFQAw%3D%3D
Some distances from this center point:
To City Hall 450 m (1476 ft), 6 min walk
To King and Bay (Financial District) 1.2 km (0.7 miles), 17 min walk
To Union Station 1.3 km (0.8 miles), 18 min walk
To the CN Tower 1.7 km (1.05 miles), 24 min walk
To Queen's Park (Ontario Legislature) 1.2 km (0.7 miles), 18 min walk