Wanstead Flats is actually the southernmost portion of Epping Forest, but most of its trees were cleared out centuries ago, so that locals could graze their cattle and other animals here. These days, it's a large area of open grassland that attracts bird-watchers, picnicking families and anyone who fancies a stroll around Jubilee Pond. If you're feeling energetic, it's also a great place for a run or kick-about on its football pitches.
On rainy days, this flat area is liable to flood, or at least get seriously muddy, so consider bringing some wellies. But in summer, it's a welcome spot to soak up some rays: make for the edge of Alexandra Lake, with two islands in the middle, for a pretty view as you sunbathe.