The majority of mobile devices nowadays harness location and orientation-sensing capabilities, permitting for sensor based Mixed Reality (MR) gaming experiences such as Augmented Reality (AR) games. Nonetheless, only few entertainment implementations of sensor based AR systems emerged, predominantly due to low precision of sensory information causing crude and jerky augmentation, significantly impacting meaningful augmentation that inevitably affects gameplay experience. In this paper, we present a novel pervasive mobile AR Location Based Game (LBG) named Time-wARpXplorer (TARX) where a seamless design approach is used in order to address the quality of augmentation. TARX comprises of a mobile client and an online authoring tool, 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. Within the game, time travel is linked to present day through the implementation of Foursquare’s checkin platform to further raise awareness of historic sites. This paper focuses on the design considerations implemented through an iterative design process and prototyping of the mobile client, of which a novel interface emerged.