Energy resilience is becoming a key requirement for future smart infrastructures, particularly in Smart City environments characterized by large-scale distribution, heterogeneous stakeholders, and long operational lifetimes. While energyefficient communication has been widely studied, integrating it into sustainable and resilient urban systems remains a challenge. This paper presents a visionary, architecture-driven perspective on energy-resilient communication systems, with a primary focus on Smart City applications. Drawing on architectural experience from the EKI-Saxony initiative, the paper introduces a reference architecture for Smart Cities that integrates energy-autonomous field devices, mobile service entities, and modular platform services via adaptive, decentralized communication mechanisms. The SmartGreenZitty concept illustrates how energy-resilient communication can be operationalized as an enabling infrastructure layer for sustainable urban services rather than as an isolated technology. Beyond Smart City environments, the paper outlines how the same architectural principles, such as energy autonomy, decentralized intelligence, and graceful degradation, can be transferred to industrial ecosystems, including smart factories, logistics, and automation systems. The presented architecture aims to support long-term, robust, and adaptable digital infrastructures across domains. This paper does not propose new communication protocols or quantitative performance evaluations, but instead focuses on system-level architectural principles intended to guide future implementation and evaluation efforts.