This article examines the planning history of Siraf, an ancient port city on the Persian Gulf in Iran, through the lens of water heritage landscape. It argues that Siraf's water infrastructure was not a product of incremental, vernacular adaptation to aridity, but the result of deliberate urban planning rooted in Sassanid imperial policy, religious cosmology, and environmental knowledge. Drawing on archaeological evidence, historical texts, and spatial analysis, it explores how water collection, storage, and distribution systems were integrated into the urban fabric and aligned with settlement growth. The paper reframes five functionally zoned components of Siraf's water landscape as products of early planning rather than passive responses. It also engages with competing historical interpretations and recent revaluations of this infrastructure as heritage. By foregrounding the role of planning in enabling urban life in a water-scarce environment, this study contributes to planning history discourse and offers insights for contemporary planners grappling with sustainability and heritage in dryland cities. Siraf's case exemplifies how ancient urban resilience emerged from engineering ingenuity and coordinated spatial and infrastructural foresight.