Awash in memories of Japanese tradition, a wooden stump conceals a soaking tub

When this wooden stump, located in the back of a Tokyo residence, is covered, it's not readily apparent what purpose it serves aside from making a rustic dining table. But the stump, made from a cedar tree roughly 200 years old, is hollow, and its core, 4 feet wide and 3 feet deep, contains a soaking tub filled with hot spring water.

Light has symbolic cleansing properties, so it's fitting that this "stump tub" sits in a fully glazed solarium, allowing bathers to submerge themselves in both water and light, says architect Kei Sano. It's also fitting, he believes, that the solarium is the vestibule to a Kura (private museum) dedicated to the work of Mukai Junkichi, an artist celebrated for his depictions of traditional Japanese thatched farmhouses.

Junkichi lived near this estate in Setagaya, a highly developed Tokyo suburb. "His paintings make us nostalgic for the good old rural life and remind us that this area was nicer, even though nowadays it's much too modernized," Sano says. Ironically, spring bathing is another tradition that's changed: The water for this tub arrives from the mountains every two weeks by way of a 4-ton tanker truck.

Architect: Sano Kei Architects

General contractor: Mizusawa Komuten

Sources: Moulder Special Company (tree stump tub manufacturer)