## 1 Introduction  
Smart cities represent a paradigm shift in urban living, leveraging advanced technologies to enhance efficiency, sustainability, and quality of life for citizens [1]. However, urban services often operate within isolated silos, each functioning independently with minimal coordination or integration. These silos emerge due to historical development, bureaucratic structures, and specialized expertise, resulting in fragmented delivery of services (e.g., mobility, waste management and street lighting). Each service typically operates within its own department or agency, focusing solely on its specific mandate and objectives, without considering the broader urban context or potential synergies with other services [2]. Breaking down these silos is essential for creating more efficient, resilient, and sustainable urban environments. The integration of Internet of Things (IoT), Digital Twins (DTs), and Virtual Reality (VR) tools plays a pivotal role in shaping the landscape of these futuristic urban environments, enabling not only optimization of municipal services, but also providing polarization of cross-domain applications [3]. The IoT serves as the backbone of smart city infrastructure, connecting devices and systems to gather and analyze data for informed decision-making [4]. IoT facilitatesthe creation of intelligent transportation systems, environmental monitoring, and smart infrastructure, contributing to enhanced resource management and reduced environmental impact [5]. For example, IoT sensors deployed in traffic lights, public transit vehicles, and roadways can communicate seamlessly to optimize traffic flow, reduce congestion, and enhance the commuter experience. Likewise, IoT-enabled environmental sensors monitor air quality, noise levels, and weather conditions, providing valuable data for urban planners to implement measures to mitigate pollution and improve overall environmental health [6]. On the other hand, DTs, virtual replicas of physical entities or processes, have emerged as powerful tools in smart city planning and management. These digital replicas enable real-time monitoring, simulation, and analysis, fostering a deeper understanding of complex urban systems and facilitating data-driven decision-making and adaptive strategies [7]. One of the key advantages of digital twins in smart cities is their ability to model and simulate various scenarios, allowing stakeholders to anticipate the impact of different interventions or policies before implementation. For example, city officials can use digital twins to simulate the effects of changes in traffic patterns, urban development projects, or environmental policies, enabling them to make informed decisions that optimize outcomes and minimize risks [8]. Furthermore, digital twins enable cities to proactively manage and maintain infrastructure assets, such as roads or public lighting, by providing real-time insights into their condition and performance [9]. Additionally, VR tools bring immersive experiences to smart cities, offering innovative solutions for urban visualization, management interfaces, citizen engagement, and training. Integrating virtual reality technology with digital twins for smart cities and IoT applications profoundly enhances data management and interpretation, promoting wider participation in urban planning and management. VR crafts a dynamic, data-driven environment that is interactive, immersive, and conducive to collaboration, effectively bridging the physical and the digital, abstract worlds [10; 11]. Additionally, it affords unique and enriched perspectives that augment contextual awareness of the represented scenarios. By superimposing extra information onto replicated scenarios, VR depers environmental/operational understanding through pertinent data and graphical representations [12; 13]. Moreover, VR boosts collaboration by facilitating interaction among users within a common space, enhancing collective deliberation and decision-making, and thereby fostering participant synergy [14; 15; 16].