A must see if you visit San Francisco, even though it is much less vibrant than, say, Madrid, Berlin or Paris gay areas (if you're expecting some crazy stuff, you won't see much apart from one or two random naked old guys on the street). Gentrification is absolute, and there are not really many "alternative" lifestyles. The Castro is not simply a "gay" neighobourhood... most of their residents are very affluent, and predominantly white gay men, so do not expect a lot of diversity. The key of The Castro's attraction is its history of LGBT rights (you feel it in every corner) and the handsome architecture. Some nice cozy cafés and restaurants provide a great atmosphere during the day. At night, the area seems to shrink to only a couple of blocks with gay venues. Fun... but remember that this is the USA, so everything tends to close really early. Too bad.
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