The park is famous for the myriad vistas that can be found across the microislands and a distinct geographical feature of drowned dendritic valleys on the Kujuku Shima Islands; sea cliffs on the Ikitsuki-jima and Hirado-jima Islands with well-developed columnar joints; wave-eroded cliffs of Cape Osezaki on the Goto Islands; and the open-sea archipelago seascape. The park also commands a view of different volcanic landforms from Hirado-jima Island to Fukue-jima Island.
Saikai National Park, like all of Japan's national parks, has no entrance fees, no opening and closing hours, and a permit is not required to enter or stay in the park. The national parks of Japan differ from national parks worldwide in that the land within the national parks is not exclusively designated for national park use and is made up of private property as well as public and protected areas. Visitors are free to enter and leave at any time.
The park boasts wide-ranging biodiversity. The shallow water is populated with beds of macrophytes, and the inner part of the bay cultivates tidal flats, making it a great breeding ground for rare species. The land area, lush with an evergreen broad-leaved secondary forest, is noted for its controlled field burning and rocky ridges.
The park is also a place for humans. The churches of the Christian faith, the whaling culture, and the military ruins of the Sasebo Naval District are some of the must-see sights.
Marked by the distinct appearance of a lava dome lined with sharply jutted andesitic agglomerates, the vicinity of the summit is inhabited by the abundant Carpinus turczaninovii hance and other plants native to the area of jutting rocks. Quercus dentate, a relict species from the ice age, thrives at the base.
Boasting the highest density of islands in Japan, the Kujuku Shima Islands represent the landscape of Saikai National Park. Due to the islands' topography and geological features, the islands are divided into north and south, and each observatory offers scenes of interesting geographical features.
This beautiful white sandy beach has been selected in both the 100 best shores and beaches in Japan. Next to the splendor of the blue ocean, the beach is also home to a natural population of Crinum asiaticum var. japonicum and Hibiscus makinoi in the rear.
Returned to the Catholic Church, this is the largest wooden church in the Goto Islands and is a World Heritage candidate.