Glimpsing into these skulls and imagining the lives of ragpickers, rope dancers, cafe divas, brothel workers, opium addicts, besotted bohemians, and flame-throwing revolutionaries, the distinguished Belgian-born historian and critic leads us through twisting ancient streets to the teeming, generally insalubrious, stomping grounds of Baudelaire, Toulouse-Lautrec, and Edith Piaf.