Sentence:  The <WSD>District</WSD> seems complacently salubrious. It is green on the Tube map, an inoffensive colour. It has not one but two bridge crossings of the Thames, which seems greedy when you think that no other <small>[underground]</small> line has even one. 
Meaning of the word marked with <WSD> tags:  The District Line of the London Underground, originally known as the District Railway.