Belsize Park is a good place for those who have the good fortune – in both metaphorical and literal sense – to live here, along with the likes of Gwyneth Paltrow, Kate Moss, Helena Bonham Carter , Sean Bean and Gallagher brothers, represented in the Parliament by Glenda Jackson. A fashionable and expensive inner-London suburb, located between the chattering-classes Mecca of Hampstead and the slightly grittier and perhaps hipper Camden Town, Belsize Park boasts impressive town-houses and apartment blocks (many houses have also been converted into flats) lining its leafy streets.
The main roads (principally, Haverstock Hill) have an abundance of fairly upmarket little shops, cafes and the like; although its fairly central position as well as an existence of a huge Royal Free hospital in its midst ensures that Belsize Park is more than an enclave of a privilege. Instead, it's one of those typically-London "villages" that give the city its specific character. It always reminded me of some parts of Oxford, possibly because of the red-brick houses and intelligentsia-and-professionals population that is generally characteristic of the whole of this part of London.
For the casual visitor and a tourist though, Belsize Park doesn't have anything special to offer. You might end up here if walking around as it's close to several more touristy parts of the city (notably Hampstead and possibly Primrose Hill) but unless you are a celebrity stalker, it's more of a place to pass through than go to.