Twitter recently unveiled a new feature that allows users to view trending topics according to city or country.
Prior to the update, Twitter users were only able to see major topics of discussion worldwide on Twitter. With more localized trending topics, users can track trends more relevant to themselves (for example, the Celtics, for Boston residents) as well as note the differences in how various areas of the world perceive a major event.
Currently, the feature is only available for major cities and countries, but Twitter is working on adding more locations.
Source: Twitter Blog