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The Wada River dam lake (August 2007). Shitamachi, part of Masuyama Castle's town, lies beneath the water.
NhrdskPublic domainWikimedia Commons

Toyama · Tonami

Masuyama Castle

増山城

Tonami, Toyama

CastleMountain castle (yamajiro)Next 100 Fine Castles No. 140

What makes this castle distinctive

To reach the mountain castle Uesugi Kenshin attacked three times, you now walk across the top of a dam.

Why?

Masuyama Castle sits on hills on the east bank of the Wada River, and it used the river itself as its outermost moat. A dam lake created on the Wada River in 1968 turned the river into a reservoir and flooded part of the old castle town on the opposite bank. Today you park at the Masuyama Jinya rest house, walk across the dam, and enter the castle through the Kabukimon trailhead gate.[1][3]

Three things not to miss

01
Ninomaru, thought to be the main bailey, with an information board (July 2007).NhrdskPublic domainWikimedia Commons

Ninomaru, the main bailey, and its turret base

Where
The heart of the castle, reached by climbing from the Kabukimon trailhead
What to look at
A wide, flat space about 90 m by 50 m, and the raised turret base (yaguradai) in its northeast corner
Why it's interesting
Old Edo-period maps label it the "second bailey," but it is the highest and largest kuruwa (bailey) in the castle, so researchers see it as the main bailey. It is guarded on all sides by other baileys: Ichinomaru, Ajichi Yashiki, Sannomaru and Mujo.[1][2][3]
Can you see it?
Visible from outsideReachable on foot by the trail. The city estimates about 30 minutes from Kabukimon to Ninomaru and back.
02
A dry moat surviving in the cedar forest (July 2007).NhrdskPublic domainWikimedia Commons

A 300-meter double trench and rows of vertical trenches

Where
Along the east and south sides of the castle's core
What to look at
Deep dry moats cutting across the ridges (horikiri), and the many parallel trenches dug down the slopes (uneijo tatebori-gun)
Why it's interesting
Medieval mountain castles without stone walls were defended by carving the earth itself. Masuyama has a double trench up to 300 m long, plus rows of vertical trenches down the slopes that kept attackers from moving sideways. The city cites how well these earthworks survive as one reason Masuyama was chosen for the Continued Top 100 Japanese Castles.[1][3]
Can you see it?
Visible from outsideVisible from the paths inside the castle. They lie among trees, so the shapes are easier to read when the leaves are down.
03
The earthen wall at the western entrance of the old castle town, across the Wada River (June 2007).NhrdskPublic domainWikimedia Commons

The castle town's earthen wall across the river

Where
The west bank, across the Wada River dam lake
What to look at
An earthen wall running north–south for about 80 m, with a moat beside it
Why it's interesting
A castle town spread along the opposite bank, with Shitamachi east of this earthen wall and Teradoimachi to the west. Shitamachi was mostly flooded by the dam lake, but excavations turned up plenty of remains from the late 16th to 17th century, showing the town was laid out under the Sassa and Maeda families.[1]
Can you see it?
Not confirmedHow to reach and view it is not described officially.

At a glance for visitors

Nearest station
from JR Tonami Station (by taxi)
Climb
Steep climb
Time neededEditors' estimate
About 30 minutes to Ninomaru and back (the city's estimate). Allow 1.5–2 hours to explore more of the castle and the castle-town earthen wall.
Admission
Not stated officially
Hours
8:30–17:00
Access
Open to visitors

The ruins are a hillside historic site open to walk freely. Park at Masuyama Jinya, cross the dam on foot, and enter at the Kabukimon trailhead. Volunteer guides are not available from December to the end of March.

Checked:

View on mapOpen in Google MapsMasuyama Castle Ruins visitor guide (Tonami City, Japanese)Masuyama Castle Ruins (Tonami digital museum, Japanese)

The story of this castle

01
Historical record

A hill where three districts meet

Masuyama Castle stands on hills about 120 m above sea level at the eastern edge of the Tonami Plain, looking out over almost the whole plain. It lies where three districts, Tonami, Imizu and Nei, meet, an important crossroads for people and goods. On its west side the Wada River winds through a deep valley that served as a natural moat.[1][2]

02
Historical record

From "Wada Castle" to a Jinbo stronghold

The area was also called Wada, and "Wada Castle," mentioned in documents from the Nanboku-cho period (14th century), is considered the first record of Masuyama. In the Warring States period the Jinbo family, deputy governors of Etchu, extended their power here, and when Uesugi Kenshin invaded in 1560, Jinbo Nagamoto abandoned Toyama Castle and moved to Masuyama.[1][8]

03
Historical record

Kenshin, Nobunaga, Narimasa, then the Maeda

Masuyama became a battleground for the Jinbo, the Ikko-ikki (armed Buddhist leagues) and the Uesugi, and after Kenshin's repeated attacks it fell in 1576. When Kenshin died, Oda Nobunaga's forces advanced and burned the castle in 1581. In 1583 it became a castle of Sassa Narimasa, one of Nobunaga's generals, and after Narimasa surrendered to Toyotomi Hideyoshi in 1585, Nakagawa Mitsushige, a senior retainer of Maeda Toshiie, moved in.[1][2]

04
Scholarly interpretation

Massive defenses carved from earth

The castle spreads over an area about 1.4 km north to south and 0.9 km east to west on the east bank of the Wada River. Two valleys divide it into three parts: Kameyama Castle and the Magojiyama fort to the north, the core in the middle, and a group of residence sites to the south. Pottery finds suggest the Jinbo laid out the basic plan, which was then greatly rebuilt and expanded under the Uesugi, Sassa and Maeda.[1][2][7]

05
Scholarly interpretation

From castle to cedar forest

Masuyama is thought to have remained in use until around the Keicho era (1596–1615). In the Edo period it became a forest owned by the Kaga domain, where the Masuyama cedar, a well-known Toyama variety, was grown. No buildings remain, but the trenches and baileys carved into the earth survive in good condition.[1][2]

06
Historical record

National Historic Site and Continued Top 100 Castle

The Tonami City Board of Education surveyed and excavated the site from 1997 to 2003, and in 2009 it was designated a National Historic Site. Local residents then launched the Masuyama Castle Sengoku Festival, and in 2010 the volunteer guide group Kuruwa no Kai was formed. In 2017 Masuyama was chosen as one of the Continued Top 100 Japanese Castles.[1][2][3]

People of this castle

Timeline

  1. by about this year

    Appears in records as "Wada Castle"[6][1]

  2. Attacked by Uesugi Kenshin, Jinbo Nagamoto moves from Toyama Castle to Masuyama[1]

  3. Uesugi Kenshin captures Masuyama[1][2]

  4. Oda forces burn the castle[1]

  5. Sassa Narimasa surrenders; Nakagawa Mitsushige of the Maeda moves in[1][2]

  6. Designated a National Historic Site[2]

  7. Chosen as a Continued Top 100 Japanese Castle[3]

Buildings and remains

The keep today

No keep was built

An earthwork mountain castle of the Warring States period that never had a keep.

The site today

No buildings remain; earthworks such as baileys, trenches and vertical moats survive in a cedar forest, and the area can be explored as Masuyama Castle Ruins Park. The Wada River is now a dam lake, and part of the castle town on the opposite bank lies underwater.

Main buildings

Site only

Ninomaru (main bailey) and turret base

The highest and largest bailey. No buildings; the leveled ground and the turret base remain.[1][2]

Site only

Double trench and parallel vertical trenches

Trenches up to 300 m long and vertical moats guarding the core's east and south.[1]

Site only

Castle town earthen wall

An earthen wall about 80 m long with a moat, on the west bank of the Wada River.[1]

Key facts

Type
Castle
Setting
Mountain castle (yamajiro)built on a mountain; expect a climbEditorial article
Period
Medieval (c.1185–1570s)Editorial article
Keep (tenshu)
No keep was builtthe castle never had a keepEditorial article
Built
1362Japan Castle Foundation
Main lords
Jinbo Nagamoto, Sassa Narimasa, Maeda clan, Uesugi clan, Oda clan, Shiba clan, Jinbō clan, Nakagawa MitsushigeJapan Castle Foundation
Abandoned
1615Wikipedia (ja)
Remains to see
Baileys / enclosures (kuruwa), Turrets or turret bases, Vertical moats (tatebori), Trench cuts (horikiri), Stone walls, Earthen ramparts, Wells, Moats, Fortified gateways (koguchi)Editorial article
Designation
National Historic Site (Masuyama Castle ruins) (2009)Editorial article
Selection
Next 100 Fine Castles No. 140Japan Castle Foundation

Visiting

Access

Open to visitors

The ruins are a hillside historic site open to walk freely. Park at Masuyama Jinya, cross the dam on foot, and enter at the Kabukimon trailhead. Volunteer guides are not available from December to the end of March.

Address

Masuyama Jinya rest house: 211 Masuyama, Tonami, Toyama 939-1402[3]

Checked: 2026-10-03

Nearest stations and how to get there

JR Tonami Station (by taxi)JR Johana Line

Steep climb

About 20 minutes by taxi from the station. From Masuyama Jinya, walk across the dam and climb the trail from Kabukimon.[4]

Checked: 2026-10-03

Hours and admission

Masuyama Jinya (rest house and toilets)
Hours
8:30–17:00
Closed
Closed for winter December 26 – March 14 (toilets included)
Admission
Not stated officially[3]
Checked: 2026-10-03
Tonami City Archaeological Center (Continued Top 100 Castles stamp)
Hours
9:00–17:00
Closed
Mondays, the 3rd Sunday of each month, national holidays (and the following day when a holiday falls on Monday), and December 29 – January 3
Admission
Free[3]
Checked: 2026-10-03

By car / parking

Enter "Masuyama-jo ato" in your car navigation, or "Wadagawa Dam Management Office" if it does not appear. Masuyama Jinya is on the left just before the office; park there. About 30 minutes by car from the Tonami IC.[3][1]

Checked: 2026-10-03
Grounds opening hours
Not confirmedChecked: 2026-10-03
Time neededEditors' estimate
About 30 minutes to Ninomaru and back (the city's estimate). Allow 1.5–2 hours to explore more of the castle and the castle-town earthen wall.
Steps, slopes and footing
A mountain castle on hills about 120 m high; expect unpaved trails with ups and downs.[1]
Wheelchairs and strollers
Not confirmedChecked: 2026-10-03
Toilets and rest
Toilets at Masuyama Jinya (closed December 26 – March 14)[3]
English signs / audio guide
There is a Japanese-language audio guide, "Masu-Navi," narrated by the castle's honorary lord, rakugo storyteller Shunputei Shota; play it from QR codes on signs in the castle, or borrow a free player. English guidance is not confirmed.[3]
Seasons
No official seasonal information was found. In winter (December 26 – March 14) Masuyama Jinya is closed and guides are not available.[3][4]
Photography
Not confirmed
Works, closures and restrictions
On Tuesday, October 6, 2026, from about 7:00 to 17:00, the walkway over the dam to the castle will be closed for a geological survey of the lake.[5]Checked: 2026-10-03

Suggested routes

30 minutes: Kabukimon to Ninomaru and back 30 min

  1. Park at Masuyama Jinya and pick up a leaflet
  2. Walk across the top of the Wada River Dam
  3. Enter the castle at the Kabukimon trailhead
  4. See Ninomaru, the main bailey, and its turret base
  5. Return the same way to Kabukimon

The time is the city's estimate for Kabukimon to Ninomaru and back; it does not include crossing the dam from Masuyama Jinya.

Around the castle

Museum

Tonami City Archaeological Center

Displays finds from Masuyama Castle and a model of the whole castle; it also keeps the Continued Top 100 Castles stamp and sells goshuin-style castle seals. Free entry. Located on the grounds of Shoto Elementary School (566 Ranjo, Tonami).[3]

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

Good for anyone who wants to learn how to read an earthwork castle with no buildings, those interested in the Uesugi–Oda–Jinbo struggle over Etchu in the Warring States period, and people who enjoy forest walks.

What makes it interesting

Once you have taken in the size and height of Ninomaru, look at how deep the surrounding trenches and vertical moats are; they show how huge these earth-only defenses were. As you cross the dam, remember that a castle town lies beneath the lake, and the view takes on a new meaning.

Before you go

It is too far to walk from a station, so go by car or taxi. Wear good walking shoes for the trails. In winter the Masuyama Jinya rest house and toilets are closed. The 100 Castles stamp is not at the ruins but at the Tonami City Archaeological Center.

Ways to enjoy it

Get a feel for the castle's layout from the leaflet and displays at Masuyama Jinya before you climb. Japanese speakers can use the Masu-Navi audio guide via QR codes in the castle for spot-by-spot commentary. To book a volunteer guide from Kuruwa no Kai, apply at least two weeks ahead.

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Open questions

Sources

  1. 1
    増山城跡(上杉謙信が3たび攻めた城)砺波市教育委員会(デジタルミュージアム砺波正倉)municipalChecked:
  2. 2
    増山城跡文化遺産オンライン(文化庁)heritageChecked:
  3. 3
    国指定史跡 増山城跡のご案内砺波市municipalChecked:
  4. 4
    増山城跡のガイドをご希望の方へ(曲輪の会)砺波市municipalChecked:
  5. 5
    増山城跡横 ダム通路の通行止(予定)砺波市municipalChecked:
  6. 6
    続日本100名城 一覧公益財団法人日本城郭協会jokakuChecked:
  7. 7
    増山城(補助資料)Wikipedia日本語版otherChecked:
  8. 8
    戦国時代編2富山市埋蔵文化財センターmunicipalChecked:
  9. 9
    List of Japan's 100 Fine Castles and the Next 100公益財団法人日本城郭協会jokakuChecked:
  10. 10
    Wikipedia「増山城」Wikipedia日本語版wikipediaChecked:
  11. 11
    Wikidata Q11429184WikidatawikidataChecked:

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

Nagasawa Nishi Castle6 km · Not yet confirmedTakayama Castle6.1 km · Not yet confirmedNagasawa Higashi Castle6.2 km · Not yet confirmedTomisaki Castle7 km · Not yet confirmedHimiya Castle7.2 km · Not yet confirmedSho Castle7.9 km · Not yet confirmed

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