With its central image of the old masturbator in the Berlin “underground” restroom, Khodasevich's poem “Under the Ground” (1923) both shocked and fascinated its readers. Khodasevich's intervention into two taboo themes in turn-of-the-century European culture—masturbation and public restrooms—is primarily self-reflexive, indicating his anxieties about the ambiguous place and status of a modernist poet and exploring the norms of poetic representation. The essay proposes to read “Under the Ground” as a site of contested and mutually commenting meanings among concerns about taboo sites of urban modernity, a self-reflexive vision of autoerotism, and aesthetic modernism with an emphasis on the shock effect. In analyzing Khodasevich's radicalization of his modernist poetics through the re-appropriation of these taboo themes, I also examine how current theorizations in the developing subfields of sexuality and urban studies that deal with masturbation and restrooms can contribute to the ongoing research on modernist authorship as understood through the figure of the poet-flâneur.