Spadium Japon is one of the largest natural hot springs in the Kanto region, housing 15 different baths and saunas, including a seasonal medicinal bath, milk bath, mineral salt sauna, open-air rooftop onsen and more. It uses spring water from Higashikurume, an extremely popular spring, known for its incredibly transparent water. It also has an impressive lineup of bedrock baths where you can relax and recharge after a hot bath.
The top floor has a lounge space with comfortable couches and 30,000 manga volumes you can read for free. There’s also a food court here where you can eat steak, ramen, banh mi and even pizza from Azabu Juban’s famed restaurant Savoy.