North Ninepin Island in 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.

North Ninepin Island'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.

North Ninepin Island’s most famous sea arch, Big Stove Arch, is a spectacular natural tunnel formed by persistent wave erosion of volcanic rock. If wave permits, kayakers can paddle through this majestic double-connected corridor, framed by towering hexagonal rhyolitic columns formed about 140 million years ago. It offers stunning coastal views and a unique geological experience within Hong Kong’s UNESCO Global Geopark.