Koyama

Talented landscape architect Kenzo Kosugi designed the lush and meticulously kept Japanese garden that this beautiful onsen is built into. Luxuriating surrounded by the greenery and prettily placed rocks is indeed heaven. There are male and female soaking pools and a central pool for all genders, as well as saunas and outdoor hot tubs. You have to be at least of thirteen years old at this spot, so the vibe is more serene than at some of the larger onsens, where children have free rein.

There are two distinctly wonderful bathing experiences at this onsen: The amber-colored water in the Golden Hot Spring is iodine-rich and naturally maintains a temperature of one hundred degrees, while the inky water of the Tokyo Black Hot Spring feels almost gelatinous and gets its color from the skin-clearing minerals. There's also a gorgeous hot stone sauna and a small selection of food in the lobby. For the complete experience, order the onsen tamago, an egg cooked in the hot spring water, which you eat with a cup of diluted apple cider vinegar.