We're looking for Europe's second-longest river in today's Geo Quiz.
Among the Central European cities it runs through is the Hungarian capital, Budapest. It's a scenic highlight of a lovely city that local officials are trying to make lovelier still...by getting rid of graffiti.
The answer is the Danube River.
Listen to our interview with the BBC's Nick Thorpe who reports that the city of Budapest this week declared war on graffiti. It's launched a long campaign to remove and discourage the graffiti.
"I'm standing on Saint Istvan Boulevard, a busy Budapest street, where the new anti-graffiti action has just started. And it has got off to a rather successful start. The walls of shops , a theatre, and residential blocks here which have been covered in graffiti for years are now looking very clean indeed. The campaign is being run by a coalition of groups, including even some graffiti artists. Who are being given more legal spaces to exhibit their work.
In response to what many see as an epidemic of graffiti, which doesn't spare buses, trains, bridges, or even churches and schools, the organisers of this campaign have established a network of companies, police, district councils, and action groups. They say that if they can clean away new graffiti quickly enough, there is less chance of it being added to. There have been previous attempts in Budapest, which failed. What this new initiative can achieve will only become clear in the months ahead."
