In this paper, we present a novel pervasive mobile game named Time-wARpXplorer (TARX) that comprises of a mobile client and an online authoring tool. The game was created to encourage visitors and locals to explore the city of Lancaster by travelling back in time and space to discover their immediate and distant surroundings. In particular, TARX combines exploration of past and present day by allowing players to warp back in time based on the players physical location. This time travel is linked to present day through the implementation of Foursquare’s checkin platform to further raise awareness of historic sites. The paper focuses on the design considerations and implementation of the novel mobile client (Time-wARpMachine) and the requirement these place on the online authoring tool (Xplorer Authoring Tool).