ABC News’ Bob Woodruff takes you on a rare trip inside North Korea as the country holds military celebrations for its Worker’s Party. Requires a recent 5" or 6" phone and a Google Cardboard virtual reality viewer. What is Google Cardboard? Cardboard is a low-cost, easy-to-get virtual reality viewer that transforms a phone into a basic VR headset. Learn more about Google Cardboard at g.co/cardboard.