Forest City For every tree felled to make room for a development another tree of the same species would be planted on the roof. Walkways connecting one roof to another would allow small animals like squirrels to move from forest to forest. The trees could also be a food source for people and filters to clean polluted air.

Ferro-cement Apartments Habitats made to resemble natural rock formations providing living space for people as well as for lizards, birds, etc. The advantages of ferro-cement are its relative cheapness and its properties as an insulator. It makes better sense to install solar panels on the roof instead of using wood-burning fireplaces implied by the chimneys shown in the illustration.

Swords into Plowshares Recycling mothballed Navy vessels as condominiums with vegetable gardens/orchards on flight deck. Schools, day-care centers, recreational centers, restaurants, swimming pools, offices and living quarters below deck. Other possible uses: homeless centers or cheap housing for the poor. Residents could supplement protein needs by fishing. Several vessels could be linked together to make a small city with one deck left as a a local airport. Floating cities... a solution to sea level rise?

Hanging Gardens Apartment building covered on its sun-facing sides with vines bearing tomatoes, cucumbers, grapes and other edibles. The building would have to be constructed with "pockets" set into the walls for soil. A design that would work well in rainy climates such as the Pacific Northwest of the US, parts of western Europe, tropical regions, etc. A system of pipes would bring water and nutrients to soil.

The key to this design is water storage. Rain must be stored somehow under the roofs or in rain barrels and groundwater pumped to rooftop storage tanks. The structural strength of a roof will determine its use as garden or as energy production.

Tree Town Genetically engineered super tree that supplies food, oxygen, building materials and living space for its human and non-human inhabitants.