how to get the boundaries of a city in KML from google maps

im trying to write a google maps application. and i wanted to only highlight one city in the world ( im using the masking method explained: https://github.com/vasile/geomask) but now im bugged with the question of how to only show the boundaries of the city as displayed in google maps. can any one suggest how to extract the boundaries of the city from google maps in KML file so that i can use the same. in my project.