A double helix staircase, said to have been commissioned by a French prince so that his wife and his mistress would never cross paths within the house, has existed at the Institut français Tokyo since 1951. On one of the staircases, you can hear the humming of the wife; on the other, the humming of the mistress. In the hall where the two staircases connect—the only point where they do—these two voices merge into a single melody.