García-García approaches St. Petri through an unusual archival object: a fragile folded-paper construction kept by Lewerentz during the building process. Rather than treating the object as marginal ephemera, the essay reads it as a condensed spatial proposition connecting origami, brick lamellae, structural balance, air, sound and bodily perception. Its theoretical contribution lies in demonstrating how a minor representational artefact can reveal architectural logic not fully available in conventional plans or photographs. The method combines archival discovery, model-making and close spatial interpretation, allowing apparently immaterial qualities—air movement, suspension, darkness, resonance—to become analytically legible. This produces a bridge between architectural history, material culture and artistic research: the archive is no longer only a repository of evidence but a site where latent operations can be reconstructed experimentally. Lewerentz’s paper object matters because it changes the scale at which the building can be understood, exposing a continuity between speculative gesture, constructional intelligence and atmosphere without reducing one to illustration of the others.