The most under-rated sense

"I'm not being funny, but my favourite smell in the world is the smell of bicycle shops - try it, you'll never look back."

found at
http://www.halfbakery.com/idea/Manly...ner#1023980502

Is there a generic Bikeshop smell ?

I know there are particular city smells. London smells very different from Birmingham. Can you recognise a city by its smell ?
Which city smells the best/worst.
Why do cities have individual smells ????