Cairo’s densified urban context has passed through several developmental phases. This article examines two of its previously developed garden suburbs that have converted over time into heavily mixed-use communities. The paper investigates the mixed-use activities occupying ground-floor levels in Zamalek and Heliopolis (Motaza division), two of Cairo’s central city neighborhoods. It aims to identify their mixed-use physical and economic features through a thorough field survey. Assemblage-thinking techniques and mapping were employed to give an empirical understanding and interpretation of how both neighborhoods work. The paper provides a provisional economic profile for each neighborhood and a proportional distribution for the ongoing activities. Also, we propose a novel approach, a preliminary threshold indicator of mixed-use activities, by examining the relation between closed-shop phenomena, entropy, and FSI measures. The study presents an introductory innovative tool for urban planners and municipalities to guide future growth in Cairo and control present mixed-use activities in other old existing areas.