The US city of Pittsburgh claims to have more bridges than any other place in the world - and don't try telling locals otherwise.

There are 446 of them, to be precise. The best known of those bridges span the two rivers, the Monongahela and Allegheny, which flow through Pennsylvania and meet in the old steel city to form the Ohio River.

Maintaining and upgrading so many structures is an expensive and time-consuming business. The state department of transport says it invests $150m (£95.5m) a year on bridges alone, while a multi-billion-dollar federal highways bill will also help in 2015.

That flow of money is helping create new construction jobs in a city where the once-dominant steel industry has been in long-term decline.

Produced for the BBC by Colm O'Molloy

You can watch all of the BBC Pop Up stories from Baton Rouge and Boulder. And visit the behind-the-scenes blog to see what the team is up to in Pittsburgh.