The Who and the Why?

I moved to Istanbul in August of 2010.  While getting lost in the city, i always noticed the ornate apartment doors.  The more i got lost, the more i noticed how unique each apartment building's door was.  
The name bab-i Humayun, is the name given to the imperial gate of the Ottoman palaces.  This was the outer most gate of the palace.  While the empire is gone, it's mark has been forever left on this imperial city.  
These decorative apartment doors are something unique to Turkey, as far as i know.  Each one has it's own character and style that changes from building to building.