Nagano Iida City
A sky-high hot spring where you can enjoy the panoramic scenery of Shinshu and the beauty lotion bath
"Sangitei Honkan, Castle in the Sky" is a Japanese-style hot spring inn in Iida City, Nagano Prefecture. Located on a small hill where Iida Castle once stood, it offers sweeping views of the city below and the distant Southern Alps. Its pride and joy is the alkaline natural hot spring known as the beauty lotion bath, with its silky texture. Guests can enjoy spectacular scenery from the open-air bath suspended in the sky or from the spacious large public bath. The property also features a mist sauna gently wrapped in mineral-rich steam and a private semi-open-air bath for unhurried, private time. With a beautiful Japanese garden that changes with the seasons, it promises a special stay that soothes the heart.

A panoramic large public bath with views over Iida City below and the majestic mountain range of the Southern Alps in the distance. Equipped with an open-air bath that feels as if you are floating in the sky, it lets you feel the clear air and rich nature of Minami Shinshu with your whole body. The smooth, alkaline natural hot spring, praised as the beauty lotion bath, gently wraps your skin.

A semi-open-air private family bath where you can fully enjoy a renowned hot spring in a private space away from the surrounding bustle. Whether with someone special or alone in quiet solitude, you can indulge at leisure in the silky hot spring, known for its skin-beautifying effects. This special bathing experience lets you enjoy the luxury of setting your own pace while bringing deep peace to both body and mind.

A mist sauna filled with fine, steam-like vapor rich in hot spring minerals that gently envelops the entire body. Its soft warmth heats you from the core without making it hard to breathe, encouraging natural perspiration. By moisturizing the skin and improving circulation, it brings deep relaxation and a pleasant warmth that lingers even after you leave the bath.
Availability and rates are shown on each booking site.
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Day-use bathing: 12:00–21:45
Bathing is allowed if tattoos are covered with stickers or if you use the fully reservation-based private bath, Nanten.
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JAPAN'S FINEST ONSEN & SAUNA
The Finest Onsen & Sauna in Japan
57 SELECTIONS
Most of what we surveyed never even made it onto this site. This book is a further cut from what did. Our editor bathed in every onsen and sauna in it, and wrote only what they confirmed on the ground.