Producer Eleanor McDowall 'Spanning the World' is a new BBC World Service series, which examines some of the stories that give bridges around the world political, metaphoric, structural or aesthetic significance.

In programme two, we visit the Ponte Milvio in Rome, a bridge which has recently become a site of romantic pilgrimage for young Italian lovers. They clip a golden padlock onto one of the bridge's ornate lampposts, stand with their backs to the Tiber and toss the key into the river as a sign of their eternal devotion.

This seemingly harmless ritual became a point of political controversy after three separate lampposts buckled under the weight of tonnes of brass and steel. Amidst fears for the safety of the ancient bridge, the mayor penalized the teenagers - a move which saw him accused of one of Italy's greatest crimes - being 'anti-love'.

Yet underneath the contemporary folklore of the 'lovers bridge' runs the story of its first incarnation - a long since destroyed version of the Ponte Milvio, which served as the focal point for one of the most important battles in the history of Christianity - the Battle of Milvian Bridge.

In this programme we examine the bridge as a site of both romantic and religious pilgrimage, exploring the art and architecture it has inspired and the imaginative space it occupies in the minds of generations of Romans.