Speaking of North pole, a friend of my dad's (now sadly passed) was stationed at a base pretty much next to the North pole. The planet wobbles a bit, so they had a ring of barrels around the area of where it might be at the moment. He and a couple of other guys from his unit used to run around the barrels every so often. He claimed it counted as "running around the world". He might have been right; we're on an oblate sphere, so the circumference goes down as the latitude goes up - this was just about as small as it could get.

No, I have no idea why those barrels were there. He didn't mention any astronomical instruments - and I'm pretty sure the concerns about the magnetic poles flipping came after the 50s. Maybe they were there just so they could say they'd run around the planet(?)