The northernmost source of the River Fleet lies 100m above sea level in the ancient woodland of Caen Wood, on a sandy ridge at the very top of Hampstead Heath. The Highgate branch of the river rises in the grounds of what is now Kenwood House, an 18th century neoclassical villa owned by top judge Lord Mansfield. The richly decoratedlibrary is especially fine, and the stuccoed facade quite magnificent. In the 1920s the property was in danger of being sold off and the estate given over to housing. But Lord Iveagh, heir to the Guinness millions, stepped in and bought the house for the nation, bequeathing with it an outstanding art portfolio that can still be seen today. For free. I was particularly taken by a Constable miniature of the local heathland and a Rembrandt self-portrait, but also enjoyed works by Vermeer, Turner and Gainsborough, and a series of Stuart portraits upstairs in the Suffolk Collection. Maybe I'll come back and do the tearooms in 20 years time.
Every summer Kenwood hosts a series of open air concerts, rather more Classic FM than Radio 3, and definitely more Radio 2 than Radio 1. Last weekend you missed Will Young, but you're not yet too late for Jools Holland, Katie Melua or the last night of the Kenwood Proms. Life is rather more quiet and sedate here for the rest of the year. Kenwood's grounds are huge, and really quite diverse. There are ornate gardens, there's untouched oak woodland, there are extensive meadows, and there are statues by Moore and Hepworth. There's also a lush green lawn leading down to an idyllic pair of lakes, although that white structure at one end is actually a wooden cut-out masquerading as a bridge. And look more carefully in the summer-browned grass, just to the south of the main terrace, and you may spot a thin meandering wiggle of earth which (in wetter weather) is one of the sources of the river Fleet. Further west, in mid-meadow, a second source originates in a fenced-off sphagnum bog. It's much more pleasant than it sounds and, if you manage to find the gated entrance, you can stand in the middle surrounded by bees, butterflies and waving marsh flowers. Magic. by bus: 210