The Nanatsugama Sightseeing Boat, known as Ikamaru, departs from Marine Pal Yobuko in Yobuko Town, Karatsu City, Saga Prefecture. This approximately 40-minute cruise takes visitors along the beautiful coast of the Genkai Sea to Nanatsugama, a spectacular natural landmark where powerful waves have carved a series of sea caves into the cliffs.
The boat has a distinctive design inspired by a squid, making the journey enjoyable even before the dramatic coastal scenery comes into view. From the sea, passengers can admire the enormous cliffs and caves at close range, experiencing a perspective that is very different from viewing them from land.
Nanatsugama is a group of sea caves formed over many years by the powerful waves of the Genkai Sea. The site is designated as a National Natural Monument of Japan and is recognized as one of the area’s most remarkable geological landscapes.
The name Nanatsugama means “Seven Cooking Pots.” It comes from the appearance of the caves, which look as though seven large cooking pots have been arranged side by side along the cliffs. In fact, there are more than seven caves, adding to the impressive scale of this natural formation.
One of the most distinctive features of Nanatsugama is its columnar jointing. This geological formation develops when lava cools and contracts, creating regularly shaped columns of rock. The columns form striking geometric patterns across the cliff faces, creating a landscape that looks almost as if it had been carefully constructed by human hands.
The largest cave has an entrance approximately three meters wide and extends about 110 meters into the cliff. When the waves are calm, the sightseeing boat may be able to approach and enter the cave. Inside, visitors can experience the mysterious atmosphere created by the sound of the waves and the shifting light reflected on the rock surfaces.
The main attraction of the Ikamaru cruise is the opportunity to see Nanatsugama from the water. As the boat approaches the sheer cliffs, passengers can look up at the enormous rock formations and observe the caves from close range.
The moment the vessel draws near the cave entrances is particularly impressive. The immense scale of the cliffs and the distinctive patterns of the basalt rock make the power of nature easy to appreciate. The refreshing sea breeze and the wide views of the Genkai Sea add to the enjoyment of the journey.
The cruise offers more than a view of the caves themselves. Along the coast, passengers can also see unusual rock formations known as Zō-no-Hana, or “Elephant’s Nose,” because of their resemblance to an elephant’s trunk.
Another notable formation is Megane-iwa, or “Spectacles Rock.” Its reflection on the surface of the sea resembles a pair of glasses, giving the rock its name. The appearance of these formations changes with the tides and lighting conditions, offering different views depending on the time of the visit.
On clear days, the contrast between the blue sea, the sky, and the dark basalt cliffs is especially beautiful, making the cruise an excellent opportunity for photography.
Marine Pal Yobuko, the departure point for Ikamaru, also operates another sightseeing vessel called Geera. This semi-submersible underwater observation boat allows passengers to view the underwater world without having to enter the water themselves.
Its observation room is positioned approximately 1.2 meters below the surface. Through large windows, passengers can watch fish swimming freely in their natural marine environment. The experience resembles visiting an aquarium, but the fish and underwater scenery are seen in the open sea.
By offering both the dramatic coastal scenery of Ikamaru and the underwater views from Geera, Marine Pal Yobuko provides two different ways to appreciate the rich marine environment around Yobuko.
The upper part of Nanatsugama is covered by extensive grassland. Observation decks and walking trails have been developed in the area, allowing visitors to enjoy panoramic views of the cliffs, caves, and sea from above.
The clifftop viewpoints are popular with visitors and photographers. The area is also known as a good fishing spot, and its natural surroundings make it a pleasant place for walking and enjoying the coastal scenery.
The cliffs and sea caves extend for approximately 1.5 kilometers along the coast. They were formed over a long period as the powerful waves of the Genkai Sea gradually eroded the hard basalt rock.
The contrast between the dark volcanic rock and the blue sea creates a dramatic landscape that reflects the immense force of the natural elements.
The Doki Cape area, where Nanatsugama is located, is associated with an old legend concerning Empress Jingū. According to local tradition, after returning from a military campaign in Korea, Empress Jingū threw earthenware vessels into the sea as a prayer for victory.
This story is said to be connected with the name Doki-zaki, meaning “Earthenware Cape.” At the northern end of the cape stands Doki-zaki Shrine, which enshrines Empress Jingū and preserves the area’s connection with the legend.
Learning about these traditions adds a historical and cultural dimension to a visit, complementing the remarkable natural scenery.
Nanatsugama can be reached by car or public transportation. From central Karatsu, the journey by car takes approximately 30 minutes.
Visitors who want to see the caves from the sea can board the Ikamaru sightseeing boat at Marine Pal Yobuko. Combining the cruise with a visit to the observation decks and walking trails above the cliffs provides a fuller appreciation of the landscape.
From Taku Interchange on the Nagasaki Expressway, the drive takes approximately 60 minutes. The journey from central Karatsu takes around 30 minutes.
From Karatsu Station on the JR Karatsu Line or Chikuhi Line, the site can be reached by taxi in approximately 20 minutes.
Alternatively, take a Shōwa Bus on the Minato–Hadosaki Line from Ōte-guchi Bus Center in Karatsu. Get off at Nanatsugama-iriguchi bus stop, then walk for approximately 30 minutes.
The Nanatsugama Sightseeing Boat offers a memorable way to experience one of Saga Prefecture’s most spectacular natural landmarks. The mysterious sea caves, striking columnar basalt formations, towering cliffs, and unusual coastal rocks reveal the remarkable landscapes created by the waves of the Genkai Sea.
Whether viewed from the boat or from the observation points above the cliffs, Nanatsugama offers a powerful reminder of nature’s ability to shape the coastline over time. A cruise aboard Ikamaru is an especially rewarding experience for visitors exploring the Karatsu and Yobuko area.