Along with the smaller St. James's and Green parks to the east, the 350-acre Hyde Park started as Henry VIII's hunting grounds. Along its south side runs Rotten Row, once Henry's royal path to the hunt—the name is a corruption of Route du Roi (route of the king). It's still used by the Household Cavalry, who live at the Hyde Park Barracks—a high-rise and a low, ugly, red block, now up for sale—to the left. You can see the Guardsmen in full regalia leaving on horseback for guard duty at Buckingham Palace at about 10:30, or come at noon when they return. Hyde Park is wonderful for strolling, cycling, or just relaxing by the Serpentine, the long body of water near its southern border. On the south side, by the 1930s Serpentine Lido, is the site of the Diana Princess of Wales Memorial Fountain, which opened in 2003 and is a good spot to refuel at a café. On Sunday close to Marble Arch you'll find the uniquely British tribute to free speech, Speakers' Corner. Though not what it was in the days before people could use the Internet to vent their spleen, it still offers a unique assortment of passionate, if occasionally irrational, advocates literally getting up on soapboxes.