* Originally built to commemorate the  British naval victory  at the  Battle of Trafalgar  over the forces of Napoleon during the  Napoleonic Wars ,  Trafalgar Square  is today a bustling public space full of tourists, relaxed Londoners and the occasional protesters. It is also London's  main venue for rallies and public celebrations  such as the countdown to New Year's Eve. * At the head of the Square stands the neo-classical  National Gallery , the  fifth most visited art museum in the world,  showcasing a collection of paintings dating back to the  13th Century . Among the  two thousand paintings  featured here, are among those done by the masters:  Leonardo da Vinci, Monet, and Van Gogh .