The department shall confer and advise with the planning body of the capital city concerning all matters affecting the metropolitan district in and within 15 miles outside the corporate limits of the city. It shall make recommendations to the governing bodies of all political units within the metropolitan district and to the Governor as to all matters of interest to the state concerning existing or new roads, boulevards and thoroughfares, street railway systems, depots, smoke prevention, parks, parkways and playgrounds, water supply, sewage and sewage disposal, collection and disposal of garbage, civic centers, and other natural or artificial physical features, and other

public improvements that will affect the character of the district as a whole.