Unzen and Shimabara: Nagasaki's Volcano Hot Springs

Explore a steaming mountain resort, a white castle town with swimming carp and a peninsula shaped by fire, all within easy reach of Nagasaki.

Published October 26, 2026 at 11:38 AM JST | By Tokyo Paul

Quick answer: Unzen and Shimabara sit on the Shimabara Peninsula in eastern Nagasaki Prefecture, centered on Mount Unzen, an active volcano in Unzen-Amakusa National Park. Unzen is a hot spring resort with steaming vents called jigoku (hells), while Shimabara is a castle town known for white Shimabara Castle and a canal of swimming carp. A direct bus from Nagasaki Station to Unzen takes about 1 hour 40 minutes.

Many visitors know Nagasaki City but have never heard of the Shimabara Peninsula, a rounded landmass pushed into the Ariake Sea by volcanic activity. It is a rewarding area for travelers who like steam, mountain scenery and quiet old towns. People search for Unzen and Shimabara together because they are usually visited as a pair: one is a mountain resort, the other a coastal castle town. This guide explains how the volcano shaped the land, what to see in each place and how to move between them.

How the peninsula was formed

The Shimabara Peninsula was built by repeated volcanic activity, beginning around 400,000 years ago, according to the Japan National Tourism Organization (JNTO) national park pages. Mount Unzen is not a single cone but a group of volcanoes, and the national park stands on several fault lines. The result is a landscape of ridges, plateaus and hot water bubbling near the surface.

That geology explains the area's appeal. Heat from the volcano warms springs, vents and steam fields, and the mountain scenery changes with each season. Mount Unzen is an active volcano, and visitors can enjoy the area safely by following signs, staying on marked paths and respecting any restricted zones.

Unzen Onsen and the jigoku

Unzen is a hot spring resort town high on the mountain. JNTO says Unzen Onsen has more than 30 sulfuric pools, and local resorts draw thermal water from them. Most facilities welcome day visitors, so you do not need to stay overnight to try a bath. Resorts and public baths vary, so choose one that suits your budget and mood.

The best-known sight is Unzen Jigoku, the "hells" of Unzen. Walkways wind around barren rocks where sulfuric steam hisses from the ground and acidic water bubbles in vents. The name sounds dramatic, but the visit is calm and interesting, and the paths are well marked. Smell and steam can be strong, so keep to the paths, and be aware that the surface near vents can be hot. Hot spring etiquette is worth reviewing before you bathe.

Mount Unzen's trails and ropeway

Mount Unzen offers gentle mountain walking for most visitors. Fugen-dake, at 1,359 meters, can be reached on a hike that gives views of Heisei-Shinzan, Japan's newest volcano. According to JNTO, Heisei-Shinzan (1,483 meters) formed during activity between 1990 and 1995 and is closed to the public because of unstable lava blocks, so views are from a distance.

The Nita Pass area has an observation point, trailheads and a ropeway to an observation deck partway up the slope. The park is attractive in several seasons: spring brings pink Kyushu azaleas, autumn brings red leaves and winter can bring frost. Check ropeway hours and trail conditions at the visitor center or on the official site, because mountain weather changes quickly.

Shimabara and its castle

Shimabara is a coastal castle town at the foot of the mountain. Shimabara Castle was built in the early 1620s and is a white, five-tiered keep that serves as the town's main landmark. Inside and around the grounds are several museums, including a hall that covers the Shimabara Rebellion of 1637 and 1638, an uprising in the region that is an important part of Japanese history. Visitors can also try on samurai and ninja clothing at the castle.

Close to the castle, the Teppo-machi district has restored samurai houses. The tone of a visit is quiet and historical, and the streets are pleasant for a slow walk. As with any castle, confirm hours and admission before you go, since they change.

Swimming carp and clear spring water

Shimabara has a charming nickname, the City of Swimming Carp. A stone-lined canal in the old samurai district carries clear spring water with around 1,500 colorful koi gliding through, an image that appeals to photographers and families. At the Shimeiso Spring Garden, visitors can drink free green tea in a tea house built on stilts above the koi pond.

Water is a theme across Shimabara. The Hamanokawa Spring is still used for washing food and dishes, and the town has public onsen baths and footbaths. Shimabara is also known for somen noodles, which are thin wheat noodles often served chilled, and trying a bowl is an easy way to taste the local flavor. Ingredients vary by shop, so ask staff if you have allergies.

Learning about the volcano

Both towns invite visitors to learn about how people live beside a volcano. The Unzen Disaster Memorial Hall in Shimabara covers the volcanic activity of the 1990s, and visitor centers in the national park explain the area's geology, plants and animals. These places add meaning to the scenery and are suitable for older children.

Nearby, Obama Onsen is a hot spring town on the coast of Tachibana Bay, described by JNTO as about 1,300 years old and as having some of Japan's hottest springs. The peninsula waters are also home to Indo-Pacific bottlenose dolphins, and short boat trips are available for those who want to see them from the Ariake Sea.

Getting there and moving around

Getting to Unzen and Shimabara is straightforward. JNTO suggests taking a JR train from Nagasaki to Isahaya, then the Shimabara Railway to Shimabara, with buses running onward to Unzen. A direct bus from Nagasaki Station to the Unzen Onsen Visitor Center takes about 1 hour 40 minutes. The Shimabara Railway opened in 1911, and the Shimabara station building was built in a castle-style design in 1989.

Ferries also connect Shimabara Port with Kumamoto, one taking about an hour and the other about 30 minutes, according to a travel guide, which makes a crossing a scenic way to continue to Kumamoto. Last sailings are in the early evening, so check current timetables. Many travelers stay a night in Unzen to enjoy the baths and a quiet mountain evening, and use a bus or rental car to connect the sights.

Planning tips

Spring and autumn are the most colorful seasons on the mountain, while summer is green and cooler at altitude than the coast. Pack layers, sturdy shoes and a towel if you plan to bathe. Hot spring facilities differ in their rules on tattoos, so check before you go.

Treat the volcano with respect: stay on trails, follow posted notices and keep to open areas. With a flexible plan, Unzen and Shimabara offer a calm and memorable mix of steam, stone walls and spring water.

Want to go deeper? Tokyo Paul's book Onsen Towns is available on Amazon.

Frequently Asked Questions

What is Unzen Jigoku?

Unzen Jigoku, or the Unzen Hells, is a field of steaming vents and acidic bubbling pools at the foot of Mount Unzen. Walkways circle the vents, and the barren rock and sulfuric steam make for a striking sight. The name means hell, but visits are calm and follow marked paths.

How do you get from Nagasaki to Unzen?

A direct bus from Nagasaki Station to the Unzen Onsen Visitor Center takes about 1 hour 40 minutes, according to JNTO. Alternatively, take a JR train to Isahaya, change to the Shimabara Railway for Shimabara, and continue by bus to Unzen. Check the current timetables.

Why is Shimabara called the city of swimming carp?

A stone-lined canal in Shimabara's old samurai district carries clear spring water and about 1,500 colorful koi carp. Visitors can drink free green tea at a stilted tea house above the koi at Shimeiso Spring Garden. Water is a central part of the town's character.

Keep Exploring

More guides from Tokyo Paul: Japan's Volcanoes: Landscapes Shaped by Fire, Mount Aso: Exploring Kyushu's Giant Volcanic Caldera and Onsen Etiquette Step by Step: Bathing the Japanese Way.