Cheonjedan is a significant altar located on Mount Halla in Jeju Island, South Korea. It is known for its historical and cultural importance, serving as a site for ancient rituals and ceremonies dedicated to the sky and nature. The name "Cheonjedan" translates to "Heavenly Altar," reflecting its spiritual significance. The altar is made of stone and is surrounded by beautiful natural scenery, attracting both tourists and researchers. It is believed to have been used by the ancient Korean people for offerings to deities, showcasing the deep connection between nature and spirituality in Korean culture.