The original Lombard Street is in the City of London, and is the traditional centre of the money market. It was so named for its banks founded by merchants from Lombardy in northern Italy.
At its western end Lombard St meets Threadneedle Street, and on that corner (also with Princes St) lies the Bank of England. This is also the intersection with numerous other streets at many angles, including Poultry and Cornhill, and underneath it all is Bank underground station. At the south-eastern end Lombard St meets Gracechurch St and turns into Fenchurch St after that.
So synonymous is it with money market that the economist and journalist Walter Bagehot (1826-1877) entitled his 1873 book on the market Lombard Street. He begins his work thus:
I venture to call this Essay `Lombard Street,' and not the `Money Market,' or any such phrase, because I wish to deal, and to show that I mean to deal, with concrete realities. A notion prevails that the Money Market is something so impalpable that it can only be spoken of in very abstract words, and that therefore books on it must always be exceedingly difficult. But I maintain that the Money Market is as concrete and real as anything else; that it can be
described in as plain words; that it is the writer's fault if what he says is not clear.
The full text is available on line at http://www.socsci.mcmaster.ca/~econ/ugcm/3ll3/bagehot/lombard.html