"Why is there grass on the roof of Parliament House?"

 Parliament House was designed by Mitchell/Giurgola and Thorp Architects, whose design was selected from 329 entries in an international competition.

One of the primary features of Parliament House is that it is built into a hill which is consistent with Walter Burley Griffin's vision for Canberra, which integrated the built and natural environment. Most importantly however, it symbolises that the government is never above the people.

diagram to help explain Why is there grass on the roof of Parliament House?