Twitter's trending topic has become a source of real-time news around the world, although there is the occasional blip. However, the thing with the trending topic has always been that only news relevant worldwide makes it there. It is not very useful if you want to know what people in your country or maybe city are tweeting about.
However, that is changing as Twitter introduces local trends. With local trend, you can get a trending topics that is relevant to the location you have choosen - a country or maybe a city. Twitter started rolling out this feature a week back but now it is available to everyone. As of now, it is available in only 6 countries and 15 countries.
To set the local trending, click on "change", below the Trending header and select the location you want to see the trending list for.
Twitter will be improving this feature with more locations, languages and other data through their API.