A free speech bastion in London's Hyde Park near the beautiful and impressive Marble Arch. Anyone with an opinion and a soapbox can (and frequently does) let it all hang out for the idly curious who gather (Sunday afternoon is a good time to go). The crowds get upset if you degrade their Queen. There are lots of Scotland Yard representatives on hand to keep order.
A recent sampling of speakers/topics included:
Your mileage may vary.