With the increasing popularity of mobile video games, game designers and developers are starting to integrate geolocation into video games. Popular location-based games such as Ingress or Pokémon Go have millions of users, yet little is known about how the use of such games influences the nature of a user's interaction with other users and their physical surroundings. To investigate how location-based games are integrated into a player's daily life, how they influence a player's mobility through the city, their perception of places and the role of human territoriality in this context, we have developed a location-based mobile multiplayer game called CityConqueror. In this paper, we present CityConqueror and the results of a study, which has focused on participants playing the game over a period of two weeks. The findings show that locationbased games can be designed to give the player the illusion of playing in the context of the "real" world rather than a virtual or hybrid game reality. Our findings also suggest that location-based games can have a strong influence on a player's mobility and perception of urban space and that human territoriality can be expressed through location-based games. Based on our findings we propose a series of design implications for the design of mobile location-based games.