Rare cave pearls in Son Doong Cave at Phong Nha-Kẻ Bàng National Park, Vietnam (© Carsten Peter/Getty Images)

【August 18 2014】There are several notable caves in Phong Nha-Kẻ Bàng National Park in Vietnam. But just five years ago, the world learned of the park’s Son Doong Cave, which is now considered the largest known cave on Earth. Aside from its immense size, Son Doong’s unique features include a forest inside the cave, a rushing river, and these limestone cave pearls.Explore breathtaking Gallery from the HuluTrip homepage over the past 5 years..