Hotel Kazusaya

The hotel's second-floor bath, Tokinoyu (時の湯), runs on the building's own filtered water, put through an in-house system that cuts the chlorine and leaves it soft on the skin. The hotel describes the feel as onsen-like, though it draws on treated tap water, not a spring. The room itself is the real draw: black walls and a wood-grain ceiling in the edoguro (江戸黒) style, screens that filter the light, and tubs cut from Towada-ishi (十和田石), a stone that turns a bright green once wet. A corridor lined in shirasu (volcanic ash) plaster leads to the bath. Hotel Kazusaya has stood in Nihonbashi-Honcho since 1891, carrying on the neighborhood's Edo-era character, a 154-room house a few minutes from Kanda and Tokyo Station.