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Mount Gassan, about 190 m high, the heart of the castle, August 2006. The main, second and third enclosures were on its summit.
MonadoCC BY-SA 2.5Wikimedia Commons

Shimane · Yasugi

Gassantoda Castle

月山富田城

Yasugi, Shimane

CastleMountain castle (yamajiro)Japan's 100 Fine Castles No. 65

What makes this castle distinctive

From the lord's mid-slope palace to the summit runs a single steep switchback, Nanamagari, climbed under fire from above: the defenses of the Amago clan's impregnable mountain castle.

Why?

Gassantoda Castle could only be attacked from three directions: Sugatani-guchi, Mikomori-guchi and Shiodani-guchi. If the lower levels fell, the defenders held the mid-slope Sanchu Goten; if that fell, they retreated to the summit of Mount Gassan. Between Sanchu Goten and the summit there is only the steep Nanamagari path. The Yasugi tourism association says attackers never reached the summit.[1]

Three things not to miss

01
The Sanchu Goten terrace, where the lord's residence is thought to have stood, June 2006.ReggaemanCC BY-SA 3.0Wikimedia Commons

Sanchu Goten and the great earthen rampart

Where
Halfway up Mount Gassan, where the paths from Sugatani-guchi and Shiodani-guchi all end up.
What to look at
The broad terrace walled in stone, the stone gateways that turn at right angles, and the great earthen rampart on the west side, about 7 m high and 130 m long, with its dry moat.
Why it's interesting
This was likely the site of the lord's residence and one of the castle's most important places. Every approach was designed to funnel here, and the stone gateways turn sharply so attackers could not charge straight in.[1][2]
Can you see it?
Visible from outsideOpen to all as a historic park.
02
Nanamagari, the winding path from Sanchu Goten up to the summit, June 2006.ReggaemanCC BY-SA 3.0Wikimedia Commons

Nanamagari, the switchback to the summit

Where
The path from Sanchu Goten up to the summit enclosures of Mount Gassan.
What to look at
The steep, winding slope and the enclosures (kuruwa) on either side of it.
Why it's interesting
It is so steep that attackers could not push up while being hit from above, and defenders could also strike from enclosures on both sides. At the top come the third, second and main enclosures, with a dry moat cut between the second and main ones.[1][5]
Can you see it?
Visible from outsideOpen on foot; wear good shoes for the steep path.
03
The statue of Yamanaka Shikanosuke on Taiko-dan, June 2006. He fought to restore the Amago family.ReggaemanCC BY-SA 3.0Wikimedia Commons

The statue of Yamanaka Shikanosuke on Taiko-dan

Where
Taiko-dan, one of the enclosures near the foot of the castle.
What to look at
The bronze statue of Yamanaka Shikanosuke (Yukimori), who fought to restore the Amago family.
Why it's interesting
Taiko-dan is said to have held a drum tower that told the time, and in the Amago era the drum is said to have summoned soldiers in emergencies. After the castle was surrendered to the Mori in 1566, Shikanosuke kept fighting to bring the Amago family back.[1]
Can you see it?
Visible from outsideFree to view.

At a glance for visitors

Nearest station
from JR Yasugi Station
Climb
Steep climb
Time neededEditors' estimate
About 2 hours to go from the foot of the mountain to the summit and back (the volunteer guides' climbing course takes 120 minutes).
Admission
Not confirmed (admission charged)
Hours
9:30–17:00
Access
Open to visitors

Open at all times, every day, as a historic park free to all. Events, commercial photography and drone flights require an application to Yasugi City. The Japan 100 Castles stamp is at the Yasugi City History Museum at the foot of the mountain (left by the entrance on closed days).

Checked:

View on mapOpen in Google MapsYasugi Travel Guide: Gassantoda Castle ruinsYasugi City: using the historic parks (Japanese)

The story of this castle

01
Historical record

A natural fortress of mountain and river

Gassantoda is a vast mountain castle centered on Mount Gassan, about 190 m high, spreading toward the Iinashi River in a horseshoe shape. The core enclosures sat on the summit, with some 500 large and small enclosures along the ridges. The Iinashi River beyond the castle town served as a natural moat. Its origins are said to go back to the Heian period, but this is uncertain.[1][4]

02
Historical record

Seat of the Amago clan

In 1486 Amago Tsunehisa retook Toda Castle and used it as his base to expand. His grandson Amago Haruhisa was appointed military governor of eight provinces across the San'in and San'yo regions in 1552, and took the Iwami Ginzan silver mine in 1556. Gassantoda was the political and economic center of the San'in region in the warring-states era.[1]

03
Historical record

Surrender to the Mori

In 1565 Mori Motonari laid siege to the castle. It was not taken by force, but in 1566, with food exhausted, Amago Yoshihisa surrendered to the Mori and handed it over. Yamanaka Shikanosuke and others later invaded Izumo to restore the Amago family but were defeated in 1570.[1]

04
Historical record

Stone walls, then abandonment

Kikkawa Hiroie, lord from 1591, added stone walls at key points and built tile-roofed turrets and earthen walls, transforming the medieval fortress into an early modern castle. After the Battle of Sekigahara the Horio family took over, but when they moved to their newly built Matsue Castle in 1611, Gassantoda was abandoned. No buildings remain, but the enclosures, stone walls and earthworks are well preserved.[1][5]

05
Historical record

Preserved as a historic park

The site became a National Historic Site in 1934 under the name Toda Castle ruins, was named one of Japan's 100 Fine Castles in 2006, and in 2018 became part of the Japan Heritage story of Izumo's tatara ironmaking. Yasugi City maintains it as a historic park open to everyone. Part of the guardhouse on Hana-no-dan has been rebuilt and serves as a rest area.[1][2][3]

People of this castle

Timeline

  1. Amago Tsunehisa retakes Toda Castle[1]

  2. Out of food, Amago Yoshihisa surrenders the castle to the Mori[1]

  3. Kikkawa Hiroie becomes lord and rebuilds with stone walls[1]

  4. The Horio move to Matsue Castle; Gassantoda is abandoned[1]

  5. Designated a National Historic Site[3][1]

  6. Named one of Japan's 100 Fine Castles[1]

Buildings and remains

The keep today

Not yet confirmed

The Japan Castle Foundation's list shows no keep. No record of a keep could be found; turret sites have been found in the summit enclosures.

The site today

The Mount Gassan area is a historic park open to everyone. No original buildings stand, but enclosures, stone walls, earthworks and dry moats remain, and part of a guardhouse has been rebuilt on Hana-no-dan. The Yasugi City History Museum is at the foot of the mountain.

Main buildings

Modern reconstruction

Guardhouse on Hana-no-dan

Partly rebuilt on excavated post-hole remains; open as a rest area.[1]

Site only

Sanchu Goten (lord's residence)

The stone-walled terrace remains.[1]

Site only

Turret at Senjo-bira

A large projecting stone wall survives, and finds including shachi roof tiles suggest a turret stood here.[1]

Key facts

Type
Castle
Setting
Mountain castle (yamajiro)built on a mountain; expect a climbEditorial article
Period
Medieval (c.1185–1570s), Early modern (1570s–1871)Editorial article
Keep (tenshu)
Not yet confirmedwhether a keep existed is still being checkedEditorial article
Built by
Sasaki YoshikiyoJapan Castle Foundation
Built
1185Japan Castle Foundation
Main lords
Horio Yoshiharu, Mōri clan, Kikkawa family, Amago clan, Toda Yoshiyasu, En'ya Kamonnosuke, Kikkawa MotoharuJapan Castle Foundation
Abandoned
1611Wikipedia (ja)
Remains to see
Stone walls, Baileys / enclosures (kuruwa), Trench cuts (horikiri), Wells, Earthen ramparts, Fortified gateways (koguchi), MoatsEditorial article
Designation
National Historic Site (Toda Castle ruins) (1934); Component of the Japan Heritage story on Izumo tatara ironmaking (2018)Editorial article
Selection
Japan's 100 Fine Castles No. 65Japan Castle Foundation

Visiting

Access

Open to visitors

Open at all times, every day, as a historic park free to all. Events, commercial photography and drone flights require an application to Yasugi City. The Japan 100 Castles stamp is at the Yasugi City History Museum at the foot of the mountain (left by the entrance on closed days).

Address

Toda, Hirose-cho, Yasugi, Shimane 692-0403[1]

Checked: 2026-10-03

Nearest stations and how to get there

JR Yasugi StationJR San'in Line

Steep climb

Take the Yellow Bus (Hirose–Yonago line) from the station to Gassan Iriguchi, then walk 1 minute. From there the site is a mountain climb.[1]

Checked: 2026-10-03

Hours and admission

Yasugi City History Museum
Hours
9:30–17:00
Closed
Tuesdays (the next day if Tuesday is a holiday)
Admission
Not confirmed (admission charged)[1][6]
Checked: 2026-10-03

By car / parking

About 15 minutes from Yasugi IC. Free parking at the Hirose Kasuri Center (44 cars, 2 buses) and the Yasugi City History Museum (10 cars).[1]

Checked: 2026-10-03
Grounds opening hours
Open at all times, every day[1]Checked: 2026-10-03
Time neededEditors' estimate
About 2 hours to go from the foot of the mountain to the summit and back (the volunteer guides' climbing course takes 120 minutes).
Steps, slopes and footing
A true mountain castle; Nanamagari from Sanchu Goten to the summit is steep, though it is now paved with stone.[1][5]
Wheelchairs and strollers
Not confirmedChecked: 2026-10-03
Toilets and rest
Not confirmed
English signs / audio guide
The Yasugi tourism website has an English page. Volunteer guides speak Japanese only.[1][6]
Seasons
Not confirmed
Photography
Commercial photography, exclusive use of the park and drone flights require an application to Yasugi City's Culture Division.[2]
Works, closures and restrictions
Roads in the area may be closed after natural disasters; check Shimane Prefecture's road closure information.[7]Checked: 2026-10-03

Suggested routes

Guided climb of Gassantoda Castle 120 min

  1. Start at the Hirose Kasuri Center parking lot
  2. Yasugi City History Museum (closed Tuesdays)
  3. The statue of Yamanaka Shikanosuke
  4. Climb through the castle site to the summit
  5. Optionally, Iwakuraji temple and the grave of Horio Yoshiharu

A guided course by the Yasugi volunteer guide association (120 minutes; 3,000 yen per guide; book at least 7 days ahead; Japanese only). Requests for weekends, holidays or Tuesdays are handled on weekdays.

Around the castle

Museum

Yasugi City History Museum

City museum at the foot of the castle covering Yasugi's ancient, medieval and modern history, and home of the 100 Castles stamp. Closed Tuesdays.[1][6]

Checked: 2026-10-03

Editors' guide

An editorial guide based on sources and confirmed information — not a first-hand visit report.

Who will enjoy it

Best for those who like reading a castle's defenses from terrain and enclosure layout rather than buildings, and for fans of the Amago clan and Yamanaka Shikanosuke. Pair it with Matsue Castle to see the shift from mountain castles to hilltop castles.

What makes it interesting

Check the defensive design at Sanchu Goten's stone gateways and great rampart, then climb Nanamagari to the summit. Looking back down the path shows just how hard an assault would have been.

Before you go

The site is free and always open, but it is a real hike, so bring good shoes and water. The 100 Castles stamp is at the history museum at the foot (closed Tuesdays; left outside on closed days). Check bus times in advance.

Ways to enjoy it

Visit the history museum first to learn about the Amago clan; the names of the enclosures will mean more on the climb. Japanese speakers can also join a local volunteer guide.

Photos

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Open questions

Sources

  1. 1
    月山富田城跡安来市観光協会(安来市観光ガイド)tourismChecked:
  2. 2
    史跡公園の利用安来市municipalChecked:
  3. 3
    富田城跡(国指定文化財等データベース)文化庁heritageChecked:
  4. 4
    日本100名城 一覧公益財団法人日本城郭協会jokakuChecked:
  5. 5
    月山富田城(補助資料)Wikipedia日本語版otherChecked:
  6. 6
    【ガイド付】月山富田城登山コース安来市観光協会(安来市観光ガイド)tourismChecked:
  7. 7
    清水月山県立自然公園島根県municipalChecked:
  8. 8
    List of Japan's 100 Fine Castles and the Next 100公益財団法人日本城郭協会jokakuChecked:
  9. 9
    Wikipedia「月山富田城」Wikipedia日本語版wikipediaChecked:
  10. 10
    Wikidata Q1039004WikidatawikidataChecked:
  11. 11
    OpenStreetMap node/2459202190© OpenStreetMap contributors (ODbL)osmChecked:

Listing status

  1. Candidate foundChecked
  2. Confirmed as a castle siteChecked
  3. Basic informationChecked
  4. In-depth articleChecked
  5. Photo rights checkedChecked
  6. Visit info checkedChecked

Castles nearby

Togamiyama Castle10.6 km · No keep recordedKumano Castle11 km · No keep recordedUshio Castle14.1 km · No keep recordedYonago Castle14.5 km · Keep lostTamatsukuri Castle16.6 km · No keep recordedMatsue Castle17.5 km · Original keep

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