Take an otherworldly journey through Hang Son Doong, the world's largest cave located in Vietnam. The cave is more than 500 feet tall, 650 feet wide, and 29,500 feet long. Video courtesy of Ryan ...

Walking into Fingal's Cave is like walking into the heart of the Earth. Here among the towering basalt columns, the visitor stands inside a lava flow. Magma that swelled up from deep in the Earth ...