One of the major challenges in second and foreign language education, is to create links between formal and informal learning environments. Mobile City and Language Guides present examples of theoretical and practical reflections on such links. This paper presents and discusses the first considerations of Mobile City and Language Guides in language centres, upper secondary schools and universities. The core concept of Mobile City and Language Guides is geotagging. Geographical locations can be geotagged either through GPS or by marking positions directly in, e.g., Google Earth or Google Maps. Students or teachers can add various kinds of information to geotags: Photos, audio, text, movies, links, vocabulary and various language tasks. This allows the student, in self-defined learning contexts, to down- and upload location-based materials with his or her mobile phone, for immediate or later processing. More and more students are able to afford mobile phones with multimedia and broadband Internet. The potentials of user-generated mobile- and web-based content are increasing. In these years, the internet is moving from the so-called Web 1.0 to the more user-centered Web 2.0, i.e. Weblogs, YouTube, Google Maps, MySpace, FlickR, etc. In an educational context, Web 2.0 represents an interesting development of the relatively monologue Web 1.0, where traditional homepages often only allow minimal interaction with the site content. This paper investigates the opportunities that Mobile City and Language Guides seem to give second and foreign language students to learn from informal, location-based, experience-based and authentic materials; and discusses how language centres, upper secondary education and universities can involve informal learning contexts through student use of mobiles with broadband and Internet technology supporting second and foreign learning. Mobile City and Language Guides is only of several possible mobile and Internet-based language educational scenarios. The challenge for the future, therefore, is to develop and implement new, meaningful and exciting scenarios that strengthen the linkages between formal and informal learning environments. (Contains 2 figures.)