Public facilities and public open space (POS) in cities are facing new challenges in the postpandemic era. Use of Japan's public libraries has been declining for years due to aging facilities and the impact of e-readers. After the pandemic, offline services are once again in crisis, and the external spaces of libraries are being utilized particularly poorly. These spaces are mainly used as parking lots with no connection to the library services themselves, which has not brought better POS to Japan's cities. Therefore, this study explores the possibility of using external library spaces from a wide-area perspective. The external space and external environment of existing libraries are then interpreted through case studies and correlation analysis. Finally, possible directions for the development of external library spaces are derived. We found that if external library spaces are developed appropriately, the POS system can be improved. This can bring libraries and cities closer together, increase intergenerational communication to better serve the aging society, and provide more economic and operational spaces for development. Ultimately, the resilience and sustainability of libraries and cities will be enhanced.