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Free Attractions In London | Hop On Hop Off Plus
"This enormous, ancient parkland is one of the best places to escape the city while at the same time catching an amazing view of it: the vista from Parliament Hill, which forms the southeast part of Hampstead Heath, is so impressive it’s actually been protected by law. Elsewhere in the park you’ll find a zoo, three swimming ponds (nominal charge which is often ignored) and plenty of quiet spots for a back-to-nature-in-the-heart-of-London picnic."