Quality and effects
Hot springs can generally be categorized into those heated by volcanoes (volcanic hot-springs) and those heated geothermally (non-volcanic hot springs). Hot springs in Ota-ku fall into the latter. When prehistoric plants decay and eventually go through coalification, they create a stratum of lignite. When the water passes through this stratum, it dissolves and absorbs the organic plant substances contained in the lignite, forming a soft and smooth hot spring, good for the skin and safe for all ages. This type of hot spring is called kuroyu, or ‘black hot spring’ for its blackish to pale brown color.
There are other types of hot springs in Ota City, including chloride springs that contain salt, and hydrogen carbonate springs, which have a similar effect to baking soda. Thus calling Ota City a hot spring “resort” is not an overstatement as you can enjoy several types of hot springs in the area.
Something you should try while you are in Ota City would be “hot spring hopping,” as it is uncommon to see this many types of hot springs within a district. First, soften and wash your skin with the black hot spring, then let it moisturize in the chloride hot spring for smoother skin. The two types of hot springs therefore function as shampoo and conditioner to your skin, offering a unique experience in Ota City.
Kuroyu, or Black hot springs
Black hot springs had only been confirmed in Baden-Baden in Germany and Tokachigawa Onsen in Hokkaido, Japan until recent developments in research and excavation technologies. Yet it remains a very rare and valuable type of hot spring, only found in several places in the world, and Ota City has one of the finest and darkest black hot springs of all.
For foreign tourists
Tokyo is actually a hidden hot spring resort, with the highest density of public bath and hot springs in Japan, and many of them are in Ota City. Having great access from Haneda Airport and Shinagawa Station, we hope you get a chance to enjoy the hot springs in Ota City.
By Shigeyuki Kanai
(Hot Springs Sommelier)