Smart cities need to ensure a secure and safe physical and digital ecosystem for the well-being of EU citizens. The EU-funded S4AllCities project aims to make cities’ infrastructures, services, ICT systems and Internet of Things more resilient while promoting intelligence and information sharing amongst security stakeholders. To achieve this, it will integrate advanced technological & organisational solutions into a market-oriented, unified cyber–physical security management framework. The system will focus on risk-based open smart spaces security management, cybersecurity shielding, suspicious activity, behaviour tracking, the identification of unattended objects, the real-time estimation of cyber–physical risks in multiple locations and measures activation for effective crisis management. This work will play a role in promoting good safety and security practices in European cities.