Answer: The Arctic Circle

After the Cold War ended and Russian maps of the Arctic Circle began circulating outside of the Russian military, shipping captains and Canadian mariners noticed something about them: they were incredibly detailed. So detailed, in fact, that they were better than official Canadian maps when it came to navigating the complex and varied waterways of the Canadian Arctic.

The incredible detail and thoroughness of the maps further reinforces the idea that Russian submarines were engaged in unauthorized patrols in Canadian waters, especially given that many of the areas so painstakingly mapped would have been inaccessible by anything but a submarine at the time the maps were created.