The Ninepin Group is part of the Sai Kung Volcanic Rock Region in Hong Kong, renowned for its extensive array of hexagonal volcanic rock columns. These columns, formed about 140 million years ago, cover an area of over 100 square kilometers, making Hong Kong home to the world's largest hexagonal volcanic rock columns group.The columns are composed of light-colored rhyolitic rock, rich in silica.

The Ninepin Group's volcanic rock formations are sculpted by relentless wave erosion, creating unique landscapes. Notable features include the Spiral Staircase Rock, Silver Bottle Sanctuary, and Big Stove Arch. These formations showcase the power of waves in shaping volcanic rocks into breathtaking natural wonders, offering stunning views and insights into geological history.

A stunning and unique natural feature in the world, these arches, such as the famous Big Stove Arch and others in the Ninepin Group, are sculpted by relentless wave erosion acting on the large, light-colored rhyolitic hexagonal columns formed about 140 million years ago. The combination of the unique hexagonal column shapes and the dramatic sea arches creates breathtaking coastal landscapes that reveal the powerful geological forces shaping the Ninepin Group region.

The Ninepin Group, particularly South Ninepin Island, is renowned for its unique volcanic rock formations shaped by relentless wave erosion. One of its most striking features is the Three Dragon Mouth, the longest sea tunnel cave in Hong Kong. This natural wonder consists of three interconnected tunnels, offering kayakers an exhilarating experience as they paddle through its majestic passages. The cave's formation is a testament to the power of sea erosion, creating breathtaking landscapes.

North Ninepin Island, part of the Ninepin Group of Hong Kong's UNESCO Global Geopark, is renowned for its stunning hexagonal volcanic rock columns formed 140 million years ago. The island features the iconic Spiral Staircase Rock, showcasing the region's volcanic history. Its geology is characterized by rhyolitic rocks rich in silica, creating a unique landscape of towering cliffs and volcanic formations.

South Ninepin Island, part of the Ninepin Group of Hong Kong's UNESCO Global Geopark, is celebrated for its dramatic sea-eroded landscapes. The island is home to the renowned Three Dragon Mouth, a series of interconnected sea tunnel caves formed by relentless wave erosion. This natural wonder, along with other sea-eroded formations like Tiger Mouth Arch and Backwash Cave, showcases the power of the sea in sculpting volcanic rocks into breathtaking caverns and arches.