The Underground Mysteries — a city questing app that allows one to reveal the mysteries of the Moscow underground using latest technologies.The application is designed for everybody living or travelling in Moscow and interested in its history or culture. It allows to search and recognise objects using augmented reality, learn new facts, receive achievements and share them with friends.Our team has designed and developed mobile applications for iOS and Android and collaborated in creating content for the mysteries. In addition, we created a backend service for content delivery and web panel to manage mysteries for the mobile app.