(Please see Geograph for further details)
221b Baker Street, in London, might have been his official address but Sherlock Holmes actually started life here in Edinburgh.
Sir Arthur Conan Doyle studied medecine at the University of Edinburgh between 1876 and 1881. One of his professors (and for whom he worked as a clerk at the ERI) was Dr Joseph Bell, who emphasized to his students the importance of observation in making a diagnosis. In later years Conan Doyle wrote to Dr Bell and credited him with being the inspiration for Holmes, "It is most certainly to you that I owe Sherlock Holmes. ... [R]ound the centre of deduction and inference and observation which I have heard you inculcate I have tried to build up a man."
Further inspiration came from Sir Henry Little-John, Lecturer on Forensic Medecine and Public Health at The Royal College of Surgeons, here in Edinburgh.
Conan Doyle was born in Picardy Place, which is why you'll find a statue of Sherlock Holmes there, holding a very nice Calabash pipe!