The largest cave on Earth is Son Doong Cave, located in the Phong Nha-Ke Bang National Park in Vietnam. It is estimated to be 5 miles (8 kilometers) long, 2 miles (3 kilometers) wide, and over 400 feet (120 meters) high at its tallest point. Son Doong Cave was discovered by a local man named Ho Khanh in 1991 and was first explored by a British caving expedition in 2009.