Sometimes called 'a city in a box', these are energy-and-carbon neutral or positive buildings that contain mixed-use development. The word 'Arcology' is a portmanteau of 'Architecture' and 'Ecology', and while they can be built without exotic technologies (see Arco Santi for example) the use of such developments as Solar Windows and Carbon-Fiber structure can greatly increase energy efficiency and earthquake safety.

Using my own home city of Portland, OR, for example, the light weight and great structural strength of the carbon-fiber structure would allow a vertical city to be built over the Willamette River between the Broadway and Fremont bridges, thus putting more housing and commercial space right next to Downtown than currently *exists* in Downtown, and addressing immediate local concerns dealing with urban gentrification, homelessness, sustainability and clean energy, earthquake safety, and issues currently outside urban planning boundaries such as climate migration.