The concept of smart cities has gained traction in academia, business, and government, describing cities increasingly composed of and monitored by pervasive computing and driven by innovation, creativity, and entrepreneurship. This paper focuses on the technological aspect of smart cities, detailing how cities are instrumented with digital devices and infrastructure that produce 'big data'. Such data enable real-time analysis of city life, new modes of urban governance, and provide raw material for envisioning and enacting more efficient, sustainable, competitive, productive, open, and transparent cities. However, the paper critically examines the implications of big data and smart urbanism, highlighting five concerns: the politics of big urban data, technocratic governance and city development, corporatisation of city governance and technological lock-ins, buggy, brittle and hackable cities, and the panoptic city. Big data refers to massive, dynamic, varied, detailed, inter-related datasets that can be connected and utilised in diverse ways. These datasets are generated through directed, automated, and volunteered data sources. Automated data generation, including surveillance, sensor networks, and the internet of things, has become central to smart city initiatives. These technologies enable real-time analytics and adaptive management of city life, but also raise concerns about data politics, technocratic governance, corporate influence, system vulnerabilities, and surveillance. The paper discusses the real-time city, where data analytics are used to manage aspects of city functions and regulation. Examples include real-time traffic monitoring, environmental data collection, and integrated data analytics centres. These systems aim to improve city management and governance but also raise concerns about data privacy, corporate control, and the potential for system failures. The paper also examines the panoptic city, where surveillance and data control raise concerns about privacy, confidentiality, and freedom of expression. The integration of data streams into a single, panoptic vantage point raises the spectre of a Big Brother society based on surveillance and dataveillance. In conclusion, while smart cities offer opportunities for efficient and sustainable urban management, they also raise significant concerns regarding data politics, technocratic governance, corporate influence, system vulnerabilities, and surveillance. The paper calls for critical interrogation of the nature and production of urban big data, the composition and functioning of urban analytics and control centres, and the implications of technocratic, corporatised, and real-time forms of governance.The concept of smart cities has gained traction in academia, business, and government, describing cities increasingly composed of and monitored by pervasive computing and driven by innovation, creativity, and entrepreneurship. This paper focuses on the technological aspect of smart cities, detailing how cities are instrumented with digital devices and infrastructure that produce 'big data'. Such data enable real-time analysis of city life, new modes of urban governance, and provide raw material for envisioning and enacting more efficient, sustainable, competitive, productive, open, and transparent cities. However, the paper critically examines the implications of big data and smart urbanism, highlighting five concerns: the politics of big urban data, technocratic governance and city development, corporatisation of city governance and technological lock-ins, buggy, brittle and hackable cities, and the panoptic city. Big data refers to massive, dynamic, varied, detailed, inter-related datasets that can be connected and utilised in diverse ways. These datasets are generated through directed, automated, and volunteered data sources. Automated data generation, including surveillance, sensor networks, and the internet of things, has become central to smart city initiatives. These technologies enable real-time analytics and adaptive management of city life, but also raise concerns about data politics, technocratic governance, corporate influence, system vulnerabilities, and surveillance. The paper discusses the real-time city, where data analytics are used to manage aspects of city functions and regulation. Examples include real-time traffic monitoring, environmental data collection, and integrated data analytics centres. These systems aim to improve city management and governance but also raise concerns about data privacy, corporate control, and the potential for system failures. The paper also examines the panoptic city, where surveillance and data control raise concerns about privacy, confidentiality, and freedom of expression. The integration of data streams into a single, panoptic vantage point raises the spectre of a Big Brother society based on surveillance and dataveillance. In conclusion, while smart cities offer opportunities for efficient and sustainable urban management, they also raise significant concerns regarding data politics, technocratic governance, corporate influence, system vulnerabilities, and surveillance. The paper calls for critical interrogation of the nature and production of urban big data, the composition and functioning of urban analytics and control centres, and the implications of technocratic, corporatised, and real-time forms of governance.