Trung Trang valley is the biggest valley on Cat Ba Island with an area of about 300 hectares, lower than sea level from 10 to 30 meters and far from Cat Ba town about 15 kilometers. Trung trang cave has 300 meters length through mountains, which is a natural cave created by heaven over two thousand years of history. Having hundreds of natural stalactites with the unique shape, the cave makes people associated with the image of the fairy. There has one range of rocks standing in parallel, if you slap hands, you will hear the sound so far away. Trung Trang Cave can contain hundreds of tourists to visit. At the Trung Trang Cave, it also has Kim Giao forest with beautiful nature, valuable economic and scientific research.