Cathedrals & great churches are among the most iconic sights of the world's towns & cities Visible from miles around the cathedrals of Canterbury St Paul's Chartres & St Stephen's in Vienna dominate their skylines Others surprise by their statistics Salisbury has Britain's tallest spire Wells the largest display of medieval sculptures in the world while King's College Chapel in Cambridge boasts the largest fan vaulting in existence Not all are ancient Dresden's reconstructed Frauenkirche opened in 2005 & Gaudi's masterpiece in Barcelona is still under construction Award-winning travel writer Sue Dobson gives us a highly personal tour of their highlights