このページはまだ翻訳されていないため、英語で表示しています。

Ryusendo Cave

Locally knownKnown to people who live here. Not in the international guidebooks.

調査・執筆 Hinato

limestone caveunderground lakecrystal blue waternatural monumentrare ecosystem

Illustration of Ryusendo Cave, 岩手県 — イメージイラスト（写真ではありません）

Ryusendo Cave is one of Japan's three largest limestone caves, famous for its underground lakes of exceptional clarity and brilliant blue water. The main lake (第三地底湖, Third Underground Lake) is 98 meters deep with transparency exceeding 40 meters — the water appears crystal-clear blue due to its purity and depth. The cave system extends over 5,000 meters, though only 700 meters are open to tourists. The accessible route includes paved walkways, lighting, and viewing platforms overlooking three underground lakes. The cave maintains a constant 10°C temperature year-round. The lakes contain rare cave-dwelling fish and bats, and the cave walls feature spectacular limestone formations — stalactites, flowstone, and calcite crystals. The blue color of the water is entirely natural, caused by light filtering through ultra-pure water and reflecting off the limestone bottom. The cave is designated a National Natural Monument and is associated with Sanriku Fukko National Park.

基本情報

営業時間

8:30 AM – 5:00 PM (last entry 4:30 PM), extended to 6:00 PM May–September; open year-round; cave maintains 10°C regardless of outside temperature

定休日: Open daily year-round; winter road conditions may occasionally affect access

料金

¥1,100 adults; ¥550 children; includes self-guided cave tour to Third Underground Lake

ベストシーズン

Year-round (cave temperature constant 10°C); spring and autumn offer best driving conditions on mountain roads

滞在目安

45–60 minutes for the self-guided cave tour; add 30 minutes for adjacent Ryusen Shindo new cave section

アクセス

アクセス情報

Iwaizumi-cho, Shimohei District. 40km from Miyako, 1 hour by car. Limited bus service (2–3 daily from Miyako). Entry ¥1,100. Cave temperature constant 10°C — bring jacket.

詳細アクセス・時間帯情報

最寄り駅

Miyako Station (JR Yamada Line / Sanriku Railway)

所要時間

Tohoku Shinkansen from Tokyo to Morioka (2 hours 10 min), then JR Yamada Line to Miyako (approximately 80 minutes); 40km by car from Miyako (about 50 minutes)

行き方

Rental car from Miyako is most practical (2–3 buses per day from Miyako Station with infrequent service); highway buses from Morioka to Iwaizumi area also available

混雑回避のコツ

The cave rarely gets very crowded due to its remote location; the most visitors arrive on summer weekends

駐車場情報

Free parking at Ryusendo cave entrance; the village is accessible year-round by car though winter chains may be needed

インサイダーガイド

The Third Underground Lake is the highlight — the viewing platform looks down on water so clear you can see 40+ meters depth. The blue color is surreal and entirely natural; no filters or lights create the effect. The water clarity rivals tropical ocean water but exists underground in total darkness. Photography allowed but the low light (even with cave lighting) requires high ISO or tripod. The cave tour is self-guided along well-maintained paths with English signage. The route takes 30–40 minutes at a leisurely pace. The first two underground lakes are smaller; the third is the spectacular one. The cave maintains 10°C temperature year-round, so bring warm layer even in summer. The cave interior is humid and paths can be slippery. The cave system extends far beyond the tourist section — advanced caving routes exist but require special permission and equipment. Ryusendo is actively studied by cave scientists. The cave-dwelling fish (Iwaizumi Doukutsu Gyo) are endemic and critically endangered. The bats hibernating in the cave are protected. The limestone karst landscape surrounding the cave includes other smaller caves and sinkholes. The village of Iwaizumi is remote and rural; visiting Ryusendo requires dedicated trip (it's not on the way to anywhere else). Combine with Jodogahama or Sanriku Coast for a full Iwate coastal trip. The cave's blue water is one of Tohoku's most unique natural phenomena. Autumn (October–November) offers best weather for the mountain drive. Winter access can be difficult due to snow.

Googleマップで見る