Sentence:  He seemed to wish to keep hold of him, and looked at him strangely, over his spectacles... when he learned that Hyacinth had taken a lodging not in their old familiar quarter but in the unexplored <WSD>purlieus</WSD> of Westminster. 
Meaning of the word marked with <WSD> tags:  The outskirts of any place; an adjacent district; the environs or neighborhood.