I quote to you from Miracle Monday, in a selection posted on the homepage of this very website:
"One hundred thirty miles south of the North Pole, there was a hollow, artificially built mountain. The mightiest hands on Earth had gathered and fused together a huge mass of granite blocks which now sat collecting snow and permafrost, hidden from anyone who might be imprudent enough to linger over this forsaken corner of the Earth. From the sky, one could see only a golden arrow the length of two Olympic pools which pointed north, presumably for the benefit of airline pilots. Only Superman could lift the sixty-ton object, slide it into a camouflaged lock set into the mountain face, and open the door bigger than most medieval cathedrals.
"This Fortress of Solitude, this repository for collectibles - the junk and the treasure of the great man's life - was the final privacy he had."
(Miracle Monday chapter 16)
I found one mention of Canada in Supermanica --Superman-robot Ajax is called into duty when Superman has to fight a fire in Canada or something.
He's been to England many times --one instance that comes to mind is a Clark Kent adventure featuring an immortal alchemist who lives inside the walls of the Tower of London (Bronze Age back-up story).
Jimmy has been to swinging London as well.