The gay center of San Francisco (and arguably the US) with a historical role that's been widely recognized by the 2008 film Milk chronicling Harvey Milk and the gay rights movement, the Castro also offers food, drinks and shopping *and* some of the hottest and best-dressed men anywhere! The neighborhood is reliably festive, and never more-so than Pride weekend :)
For a movie check out the Castro Theater - a huge Spanish Colonial affair with a pipe organ performance before most showings.
Occasionally naked men (which is legal) will wander through the neighborhood, although hardly enough to wage a political battle over.
In the surrounding areas are Dolores Park, the Lower Haight - with Twin Peaks a fairly strenuous half hour hike up the hill (Kite Hill offers similar views with less hiking).
The (in)famous and formerly massive Castro Halloween celebration has been tamped down in recent years, but still draws a crowd.
Wikipedia: http://en.wikipedia.org/wiki/The_Castro,_San_Francisco,_California
