Nanfang’ao is the largest isthmus along Taiwan’s eastern coastline. It is connected to Su-ao Harbor, with natural geographical layouts. The Black Tide that flows pass Nanfangao’s outer seas provides an abundance of migrating fish, forming natural fish grounds. The shoreline scenery of the Nanfang’ao region includes capes, reefs, cliffs, caves, isthmus, bays and beaches.
The capes, reefs, cliffs, caves, isthmus, bays and beaches in the coast nearby Nanfang’ao are formed by erosion. Land and sea are distributed wonderfully, also appearing the topography of sedimentation effect.
However, a small island acted as a barrier in front of the sandbank, causing a sandbank to form from the large amounts of sand that accumulated in behind where the wind and waves unreachable. It formed a sandbank to connect islands.
The sandbank behind the small island connects the small island and the mainland, forming an isthmus. Take a view from the mountains, the isthmus is as a row of small dunes lying horizontally across the sea, with heights reaching no more than 100 meters. There are obvious saddle landforms on the terrain, especially between the three dunes to the right, which together form the shape of a pen holder. Hence, the locals call this area “Pen Holder Mountain”.