New infrastructure added to ESA’s ESTEC technical centre in the Netherlands is helping to test how tomorrow’s smart cities will operate in practice. The HANSEL system is hosted in ESTEC’s Navigation Laboratory and allows linking to sensors across the site, providing insight into the collective networking and computing needed to get a variety of ‘intelligent elements’ to mesh seamlessly together – what the brain of a future smart city might look like. In the fairy tale of Hansel and Gretel the two children use pebbles to find their way back out of the forest (then later trying out breadcrumbs, which did not work so well). The HANSEL system looks forward to a time when smart cities are embedded with sensors that measure their positions and share them with each other, allowing the various smart city components to interact and contribute to overall accuracy and availability improvements.