Highlights: There are several huge limestone caves on Phi Phi Island. In order to protect the ecological environment of Phi Phi Island, the Thai government has only opened Viking caves for tourists to visit. There are many sea swallows inhabiting the cave, which is rich in bird's nest, so it is also called "Swallow's Nest Cave". In the nearby sea, it is also possible to see the laborious scenes of workers collecting bird's nests. The wonderful murals in the cave are engraved with murals of prehistoric humans, elephants, ships, etc., especially various ships, including various types of ancient ships from Europe, Arabia, China, etc., as well as more advanced steam ships, which are like the world. The exhibition of sea boats can imagine the busyness of this waterway in those days. However, it is said that these caves used to be the dens of Andaman pirates, so they are called "pirate caves", which makes people feel strange about these murals.