While today's galloping urbanization weighs heavily on both People and Environment and while Climate Change increases natural risks worldwide, Internet of Things Technologies stand at the forefront of the efforts toward Greener Cities. Nanosensors fully integrated into wireless sensor node may become instrumental in this field because of their small size, low cost, versatility and low power consumption. Potential applications are environmental monitoring, structural health monitoring, energy performances monitoring or people exposure monitoring. Challenges range from the manufacturing of the sensors with high reproducibility to their full integration into communicating devices, including ensuring device reliability in complex and harsh environmental conditions. Carbon nanotubes (CNT) especially are choice material toward this goal, as they have demonstrated both a very strong sensitivity to a variety of environmental parameters and a strong resilience to chemical and mechanical stress. In the present paper, we present a full proof of concept of the use of carbon nanotubes sensors for urban applications, from the manipulation of the carbon nanotubes to the application of the sensors in real life. Two specific examples are discussed, infrastructure durability monitoring and water quality monitoring. Specific methodologies for reliability analysis of carbon-based nanomaterials are also discussed.