Environmental reduplicative paramnesia (ERP) is characterized by the involuntary attribution of a false identity to a place. ERP has rarely been examined experimentally; its mechanisms therefore remain speculative. Here, we describe a patient with extended traumatic right fronto-temporal damage and severe persistent ERP, in whom we were able to modulate ERP by exposing him to various typical landmarks of the town where he was hospitalized. When landmarks were ambiguous as regards location (e.g., unknown buildings), the patient erroneously localized himself in his hometown, which was more than two thousand kilometers away. In contrast, when he visited distinct landmarks of the place where he actually resided, his ERP was immediately corrected, and spatial orientation was restored. These findings indicate that ERP may be temporarily modifiable through perception of unequivocal topographic information.