Purpose: To identify co-environmental design elements that most effectively promote intergenerational exchange in super-aged societies by comparing four communities: Share Kanazawa, Kinmokusei Urayasu, Kozenji (Japan), and the Hwacheon Community Center (South Korea). Methods: A multiple-case study collected spatial plans, operational documents, and field-observation records. Data were qualitatively coded using a three-layer typology—hardware (physical environment), humanware (people and operations), and contentware (programs)—and examined through dual lenses of physical and social integration, followed by cross-case comparison. Results: Three common antecedents emerged: (1) barrier-free circulation with open, flexible shared spaces grounded in universal design; (2) multifunctional programs supported by community facilitators that encourage voluntary, cross-generational interaction; and (3) hybrid governance in which residents, private actors, and public entities share roles and responsibilities. Differences appeared in governance models—welfare-foundation-led in Japan versus public–resident governance in South Korea—and in program orientation, with care-focused content (Share Kanazawa, Kinmokusei Urayasu) versus experiential/cultural content (Kozenji, Hwacheon). Implications: Findings yield actionable guidelines for planning intergenerational communities and building sustainable operating models across urban and rural contexts, underscoring the importance of inclusive spatial design, multifunctional programming, and collaborative governance.