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Matsunoyama Onsen: A Top Medicinal Spring with Ancient Seawater

Published May 9, 2026·3min read

Located in Tokamachi, Niigata, Matsunoyama Onsen is one of Japan's 'Three Great Medicinal Hot Springs,' alongside Kusatsu and Arima. Its water originates from ancient seawater trapped underground 12 million years ago, characterized by an extremely high salt content and potent therapeutic effects.

Table of Contents
  1. Overview
  2. Typical Spring Quality and Indications
  3. Water Characteristics and Best Season
  4. Access
  5. Nearby Sightseeing & Local Cuisine

Overview

The discovery of Matsunoyama Onsen dates back about 700 years, with a legend that it was found by a hawk healing its wounds. It is renowned for its high efficacy, earning it the title of one of Japan's 'Three Great Medicinal Hot Springs' (Nihon Sandai Yakuto).

The most unique feature of this onsen is its source: fossilized seawater from approximately 12 million years ago. This ancient water, forced to the surface by geothermal heat and pressure, is rich in minerals and has a very high salinity. The source temperature reaches a blistering 98°C (208°F), and the flow rate is abundant.

Typical Spring Quality and Indications

Chloride

The primary spring type is a Chloride Spring. The high salt content coats the skin, preventing moisture from evaporating and providing excellent heat retention, earning it the nickname 'Netsu no Yu' (Waters of Warmth). Its sterilizing properties are also said to be beneficial for cuts and skin conditions.

  • Cuts
  • Peripheral circulatory disorders
  • Sensitivity to cold
  • Dry skin
  • Atopic dermatitis

Water Characteristics and Best Season

Due to the extremely high source temperature of 98°C, most facilities cool the water to a suitable temperature using heat exchangers or by adding fresh water. Many inns offer baths fed by free-flowing spring water (gensen kakenagashi), allowing guests to fully enjoy the rich mineral content. The water is notably salty and has a faint, oil-like aroma.

Winter is particularly popular for its stunning snowscapes, characteristic of this 'snow country' region. However, the area is beautiful year-round, with the fresh green of the Bijinbayashi beech forest in spring and the golden glow of the rice terraces in autumn.

Access

Haneda Airport (HND)Travel timeabout 3 h
RouteKeikyu Line/JR to Tokyo Sta. → Joetsu Shinkansen to Echigo-Yuzawa Sta. → Hokuetsu Express/Bus.
Narita Airport (NRT)Travel timeabout 3 h 30 min
RouteNarita Express to Tokyo Sta. → Joetsu Shinkansen to Echigo-Yuzawa Sta. → Hokuetsu Express/Bus.
Tokyo StationTravel timeabout 2 h 30 min
RouteJoetsu Shinkansen to Echigo-Yuzawa Sta. → Hokuetsu Express Hokuhoku Line to Matsudai Sta. → Bus (25 min). The Japan Rail Pass is valid on the Shinkansen and JR lines.
Shin-Osaka StationTravel timeabout 4 h 30 min
RouteTokaido Shinkansen to Tokyo Sta. → Transfer to Joetsu Shinkansen to Echigo-Yuzawa Sta. → Hokuetsu Express/Bus.

Facilities with Analysis Reports

No facilities with registered analysis reports in this area yet.

Facilities Without Analysis Reports

Nearby Sightseeing & Local Cuisine

  • Bijinbayashi Forest: A beautiful forest of 100-year-old beech trees.
  • Hoshitoge Rice Terraces: A quintessential Japanese countryside scene with 200 terraced rice paddies.
  • Echigo-Tsumari Art Triennale: Artworks from the world's largest international art festival are scattered throughout the region.
  • Hegi Soba: Buckwheat noodles made with funori seaweed, giving them a unique firm texture and smooth feel.
  • Uonuma Koshihikari Rice: Enjoy delicious rice from one of Japan's most famous rice-producing regions.
  • Niigata Sake: Sample famous sake from Niigata, a prefecture renowned for its rice and breweries.
  • Muko-nage & Sumi-nuri: Unique festivals held annually on January 15th, involving throwing newly-weds into the snow and smearing charcoal.
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References

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