The paper analyzes the formation process of the historical center of Santiago, Chile, focusing on square blocks and religious buildings. Thereby, we have reconstructed the foundational state, based on the first scientific maps of the early 18th century along with the help of texts, drawings, prints, paintings, and photographs. An understanding of present day cities is inseparable from a historical perspective. Each period generates recognizable spatial and temporal layers. The urban grid, which remains apparently constant, records various transformations in its forms and nature. These transformations reflect changes in the internal organization of square blocks and their relationship to streets. It has been generally accepted that a regular and strict geometric order has been applied in the Spanish foundations of Latin America. However, this structure has been embodied in various forms, registering structural distinctions in zoning, building, and road infrastructure. We try to demonstrate that, due to urban development pressures and processes, and in spite of its historical persistence, the foundational urban grid of the Spanish Empire was less resistant to change than has been maintained in most previous literature.