It is said that money makes the world go round. But when it comes to cash, gold, diamonds or even bits of digital data, without the engines that power the world's financial systems, the money machine would grind to a halt. National Geographic Channel and host Jake Ward of Popular Science magazine take you inside the vaults of some of the world's largest and most secretive cash stashes. For more than 80 years, armored vehicles have navigated Manhattan's narrow streets carrying millions and sometimes billions in gold deposits in and out of the central bank of the United States... The Federal Reserve Bank. Manhattan's branch, one of 12 that make up the Federal Reserve System, is trusted to guard almost one-quarter of the world's entire gold supply. Just down the road, gold is given new life in New York's Diamond District. On roughly two city blocks, $24 billion in cash changes hands every year. Go behind the bargaining counters to see how everybody from low-end street sellers to high-end brokers deals in the precious metal. And whether it is handing out new bills or replacing old, the Bureau of Engraving and Printing prints, mints, protects and regulates America's print cash flow.