Can a few pieces of exercise equipment tucked into a neighbourhood park actually change a city? Since opening its first site in Gongju, South Chungcheong Province in 2021, the senior playground has spread to more than 60 locations nationwide, establishing itself as a new model of senior welfare infrastructure that brings age-appropriate outdoor spaces within walking distance of where older adults live. It is also a concrete example of the WHO Age-Friendly Cities and Communities (AFCC) framework's first domain, "outdoor spaces and buildings," realised as public infrastructure. User satisfaction and daily uptake are high, yet challenges remain: gaps in accessibility around the sites, the absence of structured programming, and limited integration with urban planning. This field note asks not only why the senior playground was built, but what a well-designed facility alone cannot do.