IN terms of respect, Birmingham is the undisputed Rodney Dangerfield of British cities. Ask a Londoner about the city, and you’re likely to receive either the blankest of stares or an unkind rendition of Birmingham’s memorable accent. American travelers, too, have mostly ignored England’s second-largest city, aside from the view from their London-bound flights. But with an only-in-Britain tapestry of vividly multiethnic neighborhoods, a postindustrial urbanity that’s gentrifying before your eyes and a food scene that can’t be ignored, Birmingham is no longer simply flyover country. Welcome to England’s heartland metropolis: big-shouldered, friendly and fun.