The increasing demand for urban development, particularly in densely populated city centers, necessitates the safe execution of deep excavations. Deep excavations not only ensure the structural safety of the planned construction but also directly affect the stability of surrounding existing buildings and infrastructure elements. In this context, retaining systems play a critical role in controlling soil deformations during excavation and minimizing environmental risks. In this study, a retaining system application carried out in a project located in Istanbul was examined in detail. The system was designed by considering soil characteristics, excavation depth, and environmental constraints. During the design stage, numerical analysis methods (Plaxis 2D) were employed. The analyses demonstrated that the retaining system is safe and adequate in terms of horizontal displacements, internal force distributions, and stability conditions. The results indicate that the retaining system design is both economically and technically feasible. This study provides a valuable reference for future deep excavation projects under similar soil conditions, offering guidance for engineering practice as well as the integration of field observations with design approaches.