In the study of seventeenth-century fortifications, the geometric precision of military architecture has often overshadowed the design of residential spaces within bastion castles. This research aims to bridge this gap by applying proportional analysis to these inner spaces, demonstrating that the principles of Renaissance architecture—often associated with grand villas and palaces—also influenced the residential areas within military structures. Architectural design often relies on specific proportions to create aesthetically pleasing and functional spaces; thus, this study seeks to automate the analysis of room proportions within the architectural layout of bastion castles, comparing them against classical standards. By loading architectural data, calculating room dimensions, and identifying the closest classical proportion for each room, his study highlights how the elegance of Palladio’s and Serlio’s principles permeated these fortified environments. This article presents a detailed workflow for analyzing architectural proportions within a given layout. Using Python libraries for mathematical computations and JSON for data handling, the methodology leverages the Grasshopper add-on for Rhinoceros to interact with pre-modeled spaces in CAD and visualize results. Each room’s dimensions are analyzed to calculate proportions, determining the closest classical ratio and quantifying proportion errors to assess alignment with classic standards. These results are visually highlighted within the Rhino interface. This workflow and code can be applied broadly to analyze the inner voids of any palace or residential space, offering valuable insights into the architectural design of various historical structures.