Rapid urbanization and growing environmental challenges demand the use of sustainable materials, which has become a key aspect of contemporary architectural and engineering design. Recycled steel stands out due to its ability to retain mechanical properties through multiple recycling cycles while significantly reducing energy consumption and carbon emissions compared to primary production. This paper examines the potential of recycled steel in architecture and construction, focusing on its role in structural systems and spatial design. Selected case studies, including Hearst Tower, Olympic Stadium, and Empire State Building, illustrate diverse approaches to its application, from advanced structural concepts to adaptive reuse strategies. The research is based on a comparative analysis of structural systems, levels of recycled material use, and their impact on energy efficiency and overall sustainability. Particular attention is given to the relationship between structural logic, economic considerations, and architectural expression. The findings suggest that recycled steel not only reduces environmental impact but also enables the development of flexible, adaptable, and resource-efficient structures, positioning it as a key material in sustainable and circular architecture.