Groningen is the Netherlands' northern secret — a student city with a medieval tower, a world-class museum, and a hidden alleyway that's been there since the 1400s. This app-led scavenger hunt takes you through Groningen on foot, using phone-based riddles to guide you from one landmark to the next. No guide, no fixed start time. • Chase riddles to the Martinitoren, the Groninger Museum, and the medieval Papengang — eight centuries in one...