SynapCity is a speculative design project and exhibition envisioning a future where cities are powered by human thoughts, transforming cognitive activity into renewable energy. It explores the design of urban systems that harvest thought-energy, reimagining how cities function and challenging societal norms around privacy, ethics, and sustainability. The exhibition immerses visitors in this futuristic world, showcasing thought-energy grids and interactive installations where emotions and thought patterns influence urban systems like lighting and transport. Through these experiences, SynapCity raises critical questions about the ethical implications of using thought as an energy source and encourages visitors to participate in co-creating future scenarios. The project invites reflection on how neuro-technologies might reshape cities, governance, and human relationships in the decades to come.