The Mandarin dialect spoken in the Beijing/Tianjin area, this is supposedly what standard Mandarin is based on. Unfortunately, Bejingese is so heavily accented that it is quite difficult to understand. Pronounciation is indeed the same as standard Mandarin, but the locals have an annoying habit of adding an "r" after every major character, making their speech somewhat similar to a continuous dog-like growl. Tongue-curling is also overused, as are guttural noises (for unknown reasons).

In essence, anyone who knows Mandarin can speak Beijingese, you just have to growl like a mutt when you talk. And wave your hands around a lot, like Italians. Northern Chinese do that for some reason. Maybe it warms their hands or something.

Beijingers are full of ego, so they often refer to their dialect as "standard Mandarin", and that is met with ridicule by the other 1 billion Chinese. When the nasty Beijing dog accent is removed, then it is standard Mandarin, and any Southerner can speak that better than the Northerners. The xenophobic Beijingers often try to enforce their rule upon others (apparently, since Beijing is the capital it makes them superior), but nobody listens to their doglike ravings. Then again, I speak as a Cantonese.

I am uncertain of the local variations in the Bejing dialect, I do know it changes very little in Tianjin. Around the area there's the Shandong dialect (a wacky mixture of Jiangsu and Beijing), and further to the north are the Mongolians, who speak a language of their own.