Foursquare is a location-based social network. Its users can check in to venues using their smartphones or computers to report their current location to their Foursquare friends.
If users want to check in to a venue that has not yet been added to Foursquare, they can create an entry for that venue on the Foursquare page. As a result, Foursquare makes available a huge number of points of interest (POI) that may be accessed through other apps, too.
BlindSquare uses this wealth of data to inform you about your environment.