Exeter, UK, holds a secret beneath its bustling streets: a 390-meter network of medieval tunnels, some as narrow as 430mm. These 14th-century passages, designed to house lead pipes for fresh drinking water, are the only ones of their kind open to the public in the UK. When asked to survey these historical tunnels and precisely tie them to the topography above, Exeter-based Benchmark Surveys knew it was the kind of complex challenge they excelled at. This remarkable heritage project was delivered successfully, thanks to a fully integrated Trimble workflow.