Every government building should have a green roof - this will not only be a beautification project, but can also significantly cut down on energy usage.
From the Wikipedia (http://en.wikipedia.org/wiki/Green_roof) entry:
-Reduce heating (by adding mass and thermal resistance value)
-Reduce heat loss and energy consumption in winter conditions.
-Reduce cooling (by evaporative cooling) loads on a building by fifty to ninety percent
especially if it is glassed in so as to act as a terrarium and passive solar heat reservoir — a concentration of green roofs in an urban area can even reduce the city's average temperatures during the summer
-Reduce stormwater run off— see water-wise gardening
Natural Habitat Creation — see urban wilderness
-Filter pollutants and carbon dioxide out of the air which helps lower disease rates such as asthma
-Filter pollutants and heavy metals out of rainwater
-Help to insulate a building for sound; the soil helps to block lower frequencies and the plants block higher frequencies
If installed correctly many living roofs can contribute to LEED points