It is difficult, if not impossible, to name an important work of literature as heavily imbued with mathematics as Bely's Petersburg. This singular aspect of the novel has not escaped the attention of historian nor literary scholar, but nonetheless a “close reading” from a mathematician's eye seems not to have been undertaken previously. In doing so, we find an amazingly rich array of mathematical manifestations and allusions. Bely's father is caricatured for his pedantry, absent-mindedness, and penchant for abstraction, yet the structure of the novel itself reflects the father's universal faith in discontinuity. Poetic shadows of Cantor's work on set theory, countability, and infinity appear in the novel and take on a Symbolist meaning in the context of the Moscow Mathematical School's religiously inspired and mystically driven work on set theory and measure theory. We interpret Bely's fantastical description of the streets in Petersburg in terms of spherical and projective geometry. We find striking similarities between Bely's treatment of a spiritual visitor from the fourth dimension and Abbott's famous Flatland, in addition to a couple passages exhibiting a slight foreshadow to Borges' very mathematical short story Library of Babel.