Nulchado is a small island located to the northeast of Gadeokdo, the largest island in Busan. The island has many high mountains with mostly steep slopes, and has a complex coastline with small inlets and bays. The Nulchado area comprises the Cretaceous Yucheon Group and the Bulguksa Granite. The Yucheon Group is composed of volcanic complexes, mainly andesite and andesite volcanic breccia. At the geosites in Nulchado, you can observe geological features such as andesitic volcanic breccia, andesitic lava, hornblende granite diorite, and Quaternary marine terraces, as well as various coastal landforms, such as sea cliffs, sea caves, headlands and bays, and shingle beaches, and historical heritages, such as the Saebaji military tunnel built by the Japanese army during the Pacific War.