From the mouth of the Potomac River, we trace kilometres of spectacular waterway - where America's north meets south. Inland, high above Washington DC - we take a whirlwind tour of this historic and cultural crossroads. With rare permission from the Secret Service, TSA and FAA, we soar above Washington's no-fly zone - capturing crystal clear images of the architecture and breathtaking monuments of America's Capital - including the Washington Monument, Lincoln Memorial - and the White House. Outside the city, we trace the natural surroundings of one of America's largest cities - from Shenandoah National Park to the spectacular depths of the Luray Caverns.