nmcul
I have missles
Unrestricted sea voyaging. In Civ I can take my caravels to the Arctic without any ill effects. In reality they would freeze their 15th-century butts to death. And if they weren't killed by exposure, they could be attacked by polar bears or rabid penguins. Even fairly modern ships might perish in the waters near the icecaps. ("Iceberg, dead ahead!")