Three-Dimensional Analysis of a Large Roman Cistern: Hydraulic Study of the Sierra Aznar Water Management System

Accurate three-dimensional documentation has become an essential tool for the analysis, interpretation, and preservation of archaeological heritage, particularly in the case of large and complex architectural remains. This paper presents a high-resolution three-dimensional documentation and quantitative study of the Great Cistern of Sierra Aznar, a major Roman water-storage structure located in Arcos de la Frontera (Cádiz, southern Spain). A geometrically reliable three-dimensional model was generated through the integration of image-based photogrammetry and terrestrial laser scanning, ensuring high spatial resolution and complete geometric coverage. The resulting model provided the basis for detailed metric analyses, including planimetric documentation, estimation of maximum storage capacity, and assessment of sediment accumulation within the structure. The results indicate that the cistern had an estimated storage capacity of approximately 2180 m3, while sediment deposits currently occupy nearly 37.5% of its original volume, offering valuable evidence for the long-term evolution and post-depositional history of the monument. In addition, the spatial and altimetric relationships between the cistern, nearby sedimentation basins (piscinae limariae), and an associated fountain are consistent with a coordinated water-management landscape, although direct hydraulic connections are not preserved. The Great Cistern of Sierra Aznar is thus presented as a significant archaeological case study illustrating how rigorous three-dimensional documentation can support quantitative analysis, contextual interpretation, and the long-term preservation of complex hydraulic heritage.