The bliss of a pH 9.7 strongly alkaline lotion bath and a source-water free-flow cold plunge bath
Kanagawa Atsugi City
"Nanasawasou" is a standalone inn with natural hot springs, nestled at the foot of the eastern Tanzawa mountains in Atsugi City, Kanagawa Prefecture. Its greatest feature is a simple hot spring with an exceptionally high alkalinity of pH 9.7, among the highest in Japan. Thanks to its smooth, lotion-like feel on the skin, it is also known as a lotion bath and is said to have outstanding beautifying effects that leave the skin silky and refined. The sauna, renewed in 2023, is a full-fledged setup equipped with a HARVIA stove, where you can enjoy a pleasant sweat while wrapped in the scent of wood. For cooling down after the sauna, there is a cold plunge bath using the source water exactly as it comes from the spring. In summer it is gently refreshing, and in winter it becomes piercingly cold, allowing you to enjoy nature's blessings with your whole body. Along with outdoor bathing surrounded by magnificent nature, it offers the ultimate therapeutic hot spring experience that deeply soothes both body and mind.
TypeNatural Hot Spring
A superb beautifying hot spring boasting an astonishing alkalinity of pH 9.7, among the best in Japan. It is characterized by its smooth, silky texture, as if you were bathing in lotion, and helps wash away unwanted dead skin cells. You can fully enjoy its rich spring quality in the rock open-air bath and reclining bath, making it truly the lotion of the earth.
Sauna TypeDry Sauna
Stove TypeConvection Stove (Sauna Stone)
Capacity4people
A full-scale sauna created through the 2023 renovation, equipped with a HARVIA stove. The compact room, filled with the warmth of wood, retains heat well and encourages deep perspiration with robust heat. A new charm of Nanasawasou, where you can enjoy luxurious sauna sessions while quietly facing yourself in a calm environment.
Water QualityHot Spring Water
Capacity2people
The facility's strong alkaline simple hot spring, which is its source water, is used lavishly in free flow exactly as it is, without being heated. It is characterized by a unique slippery feel and a smooth touch derived from the spring's mineral components, and even in the cold there is a sense of gentleness. You can experience blissful cooling while savoring the natural delight of seasonal changes in water temperature.
Closed Days: None
〒243-0121 1830 Nanasawa, Atsugi City, Kanagawa Prefecture
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more
The bliss of a pH 9.7 strongly alkaline lotion bath and a source-water free-flow cold plunge bath
Kanagawa Atsugi City
"Nanasawasou" is a standalone inn with natural hot springs, nestled at the foot of the eastern Tanzawa mountains in Atsugi City, Kanagawa Prefecture. Its greatest feature is a simple hot spring with an exceptionally high alkalinity of pH 9.7, among the highest in Japan. Thanks to its smooth, lotion-like feel on the skin, it is also known as a lotion bath and is said to have outstanding beautifying effects that leave the skin silky and refined. The sauna, renewed in 2023, is a full-fledged setup equipped with a HARVIA stove, where you can enjoy a pleasant sweat while wrapped in the scent of wood. For cooling down after the sauna, there is a cold plunge bath using the source water exactly as it comes from the spring. In summer it is gently refreshing, and in winter it becomes piercingly cold, allowing you to enjoy nature's blessings with your whole body. Along with outdoor bathing surrounded by magnificent nature, it offers the ultimate therapeutic hot spring experience that deeply soothes both body and mind.
TypeNatural Hot Spring
A superb beautifying hot spring boasting an astonishing alkalinity of pH 9.7, among the best in Japan. It is characterized by its smooth, silky texture, as if you were bathing in lotion, and helps wash away unwanted dead skin cells. You can fully enjoy its rich spring quality in the rock open-air bath and reclining bath, making it truly the lotion of the earth.
Sauna TypeDry Sauna
Stove TypeConvection Stove (Sauna Stone)
Capacity4people
A full-scale sauna created through the 2023 renovation, equipped with a HARVIA stove. The compact room, filled with the warmth of wood, retains heat well and encourages deep perspiration with robust heat. A new charm of Nanasawasou, where you can enjoy luxurious sauna sessions while quietly facing yourself in a calm environment.
Water QualityHot Spring Water
Capacity2people
The facility's strong alkaline simple hot spring, which is its source water, is used lavishly in free flow exactly as it is, without being heated. It is characterized by a unique slippery feel and a smooth touch derived from the spring's mineral components, and even in the cold there is a sense of gentleness. You can experience blissful cooling while savoring the natural delight of seasonal changes in water temperature.
Closed Days: None
〒243-0121 1830 Nanasawa, Atsugi City, Kanagawa Prefecture
Gender Access
Gender Separated
Curated by an expert who visits onsen and sauna facilities every day and has explored 300+ locations — only facilities confirmed to be truly exceptional are featured.
Learn more