Sentence:  When this old world starts getting me down/ And people are just too much for me to face,/ I climb way up to the top of the stairs/ And all my cares just drift right into space/ On the <WSD>roof</WSD>, it's peaceful as can be/ And there, the world below can't bother me... 
Meaning of the word marked with <WSD> tags:  The top external level of a building.