S1, E4: From stunning heights, witness the mountains, rivers, and people that make up China’s great interior. Visit celebrations at the center of the Buddhist world and on the edges of river cities, soar over the world’s most famous peak 29,000 feet in the air, and dive into an ancient city submerged under a lake. China’s heartland is a place where urban and rural communities embrace the challenges of a changing, 21st century world.