Securing a border is often a top priority for national security. Yet sometimes these borders are so secure, they are just as effective at keeping people out, as they are at keeping people in. Today we'll look at some of the most secure borders in the world, and explain why some of them are so difficult to cross. From well known countries like North Korea, to the newly conflict tested borders of Ukraine, Russia, Palestine, and Israel, there's plenty of borders that are worth examining.