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The emerald-green 'Atera Blue' clear stream of Atera Valley
Atera Valley — Atera Blue

Atera Valley & the "Atera Blue"

Okuwa Village, Kiso, Nagano. A white granite riverbed catches the sunlight, and the water glows an otherworldly emerald-green. A 10-minute walk from Aterasou — the story of a clear stream that runs through the Japan Heritage Kisoji.

An 'Atera Blue' pool framed by granite cliffs and the Kiso five-tree forest, Atera Valley
The Legendary Clarity A flowing jewel — "Atera Blue"

Atera Valley is sometimes called a flowing jewel — an emerald-green clear stream. The white granite riverbed catches the sunlight, and the water glows an almost dreamlike blue. Locals have long known this colour as "Atera Blue".

Look down and you can see every pebble on the riverbed through water so clear it leaves you speechless — and this stream runs right beside Aterasou. Follow the roughly 6.3 km walking trail upstream and you reach Senjojo, Inugaeri-no-Fuchi, Unari Island, Kumagafuchi, Ushigafuchi, and finally Rokudan-no-Taki (Six-Tier Falls). The Atera River flows quietly through a national forest of the five sacred Kiso trees.

日本遺産 Certified by the
Agency for Cultural Affairs
Kisoji — Japan Heritage The Japan Heritage Kisoji

Japan's Agency for Cultural Affairs designates stories that convey the nation's culture and traditions through the historical charm of a region as "Japan Heritage". The Kisoji road — along which Atera Valley lies — is one of them.

"The Kisoji is all in the mountains"— Guarding the mountains, living with the mountains —

Bigan-sui — The Sacred Spring "Bigan-sui", the hidden spring of Atera

At the mouth of the valley, beside the Atera Bridge over the Kiso River, a famed spring wells up endlessly — "Bigan-sui". Nurtured by the national forest of the five sacred Kiso trees, this pure water seeps from the bedrock and never runs dry.

Clear in every age, it has been selected as one of Shinshu's celebrated and hidden waters. On your journey, take a sip and feel the blessing of the Kiso forest.

Selected — Shinshu's Famed & Hidden Waters
The Bigan-sui spring welling from the rocks deep in the forest, flowing into a wooden trough The wooden sign of 'Bigan-sui', the famed spring of Atera Valley, with its origin story
Poems by Shimaki Akahiko The poems of Shimaki Akahiko

In June 1907, the poet Shimaki Akahiko travelled the Kisoji with Ito Sachio and spent a night at Atera Onsen. These are the five poems he composed there.

京の山 長良夏川 すずしけど 木曽の林に 思入りたりCool though the mountains of Kyoto and the Nagara's summer river — still my heart is drawn into the forests of Kiso.
山深く わけ入るままに 谷川の 水きはまりて 家一ツありDeeper into the mountains I press, until the valley stream comes to its end — and there stands a single house.
湯の宿を 夕おとなへば 裏山を 人下り来る 湯守りなるらしWhen I call at the hot-spring inn at dusk, someone comes down the back mountain — the keeper of the spring, it seems.
夕川の 水のにぎちの 石に立つ 真裸人に 月出でにけりOn a stone amid the evening river's flow stands a naked figure — and the moon has risen.
ひろらなる 囲炉裏かこみて 山人と ものかたりおれば 窓に月出づGathered around the broad hearth, talking with the mountain folk — the moon rises at the window.

Aterasou's natural hot spring, "Atera Onsen", rises here — the very place where Akahiko spent his night.

Four Seasons The four seasons of Atera Valley
Spring in Atera Valley, fresh greenery and magnolia

Spring

Magnolia and azalea bloom, fresh greenery dazzles and wild vegetables sprout — the valley at its most youthful.

Summer river play in Atera Valley

Summer

Green leaves and white clouds. Drift on a tube, leap from the rocks, chase fish with a mask — blue shimmering between light and shadow.

Autumn foliage in Atera Valley

Autumn

The song of insects, silver grass, and autumn leaves. Brocade mountains mirror in the emerald water — the valley's finest view.

Winter snow and ice in Atera Valley

Winter

Snow paints the scene like an ink-wash painting. In the stillness, crisp air and the blue stream welcome the traveller.

Access From Aterasou to Atera Valley
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About 10 min on foot

Roughly a 10-minute walk from Aterasou to the valley entrance (Atera Bridge) — a perfect morning stroll.

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About 2 min by car

About 2 minutes by car. From the Chuo Expressway Nakatsugawa IC, head north on Route 19; also reachable from JR Nagiso and Nojiri stations.

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Cycle in summer

During the summer car-restriction period, walking or a rental bicycle is best — gliding through fresh green air.

☀️ About summer private-car restrictions
In a typical year, from mid-July to the end of August, private cars are not allowed inside Atera Valley (car restrictions). During this period, please come on foot or by rental bicycle. For the latest information, please check the official Okuwa Village website.

Stay beside the Atera Blue.

Aterasou is a 10-minute walk from Atera Valley. We welcome your Kiso journey with the natural "Atera Onsen" hot spring and clear-stream river-fish cuisine. Room-only from JPY 8,000.