Mega Structure - New York Subway

For over 100 years the New York Subway has been growing beneath the most populated city in The United States. In 2014 figures just released show over 6.1 Billion rides on the subway were taken. But as this National Geographic documentary shows keeping the largest transit system in the world going requires military like planning and constant maintenance. The subway faces constant challenges as it runs under roads, rivers and skyscrapers with structural damage and the threat of fire and flooding a huge concern. In the documentary we see the history of the New York subway system as well as what goes on behind the scenes to keep the trains running in the City that never sleeps.