Smart Cities evolve into complex and pervasive urban environments with a citizens’ mandate to meet sustainable development goals. Repositioning democratic values of citizens’ choices in these complex ecosystems has turned out to be imperative in an era of social media filter bubbles, fake news and opportunities for manipulating electoral results with such means. This paper introduces a new paradigm of augmented democracy that promises actively engaging citizens in a more informed decision-making augmented into public urban space. The proposed concept is inspired by a digital revive of the Ancient Agora of Athens, an arena of public discourse, a Polis where citizens assemble to actively deliberate and collectively decide about public matters. The core contribution of the proposed paradigm is the concept of proving witness presence: making decision-making subject of providing secure evidence and testifying for choices made in the physical space. This paper shows how the challenge of proving witness presence can be tackled with blockchain consensus to empower citizens’ trust and overcome security vulnerabilities of GPS localization. Moreover, a novel platform for collective decision-making and crowd-sensing in urban space is introduced: Smart Agora. It is shown how real-time collective measurements over citizens’ choices can be made in a fully decentralized and privacy-preserving way. Witness presence is tested by deploying a decentralized system for crowd-sensing the sustainable use of transport means. Furthermore, witness presence of cycling risk is validated using official accident data from public authorities, which are compared against wisdom of the crowd. The paramount role of dynamic consensus, self-governance and ethically aligned artificial intelligence in the augmented democracy paradigm is outlined.

智慧城市发展成为具有公民授权以实现可持续发展目标的复杂而普遍的城市环境。在当今社会媒体过滤泡沫，虚假新闻以及利用这种手段操纵选举结果的机会时代，重新定位公民在这些复杂生态系统中的选择的民主价值观已成为当务之急。本文介绍了一种增强民主的新范式，该范式有望使公民积极参与更加知情的决策，从而增强公共城市空间。提出的概念的灵感来自雅典古代集市的数字化复兴，这是一个公共演讲场所，一个波利斯（Polis），市民聚集在那里积极地思考和集体决定公共事务。提议的范例的核心贡献是证明证人在场的概念：使决策者提供可靠的证据并证明在物理空间中所做的选择。本文展示了如何通过区块链共识来解决证明证人在场的挑战，以增强公民的信任度并克服GPS本地化的安全漏洞。此外，还引入了一个新颖的平台，用于在城市空间进行集体决策和人群感知：Smart Agora。它显示了如何以完全分散和保护隐私的方式对公民的选择进行实时集体测量。通过部署去中心化系统，以群众感知运输工具的可持续使用来测试见证人的存在。此外，使用来自公共机构的官方事故数据验证了证人存在骑车风险，并将其与人群的智慧进行了比较。