The Ancient Hula Hoop Buildings of China
Those exterior walls are rammed earth, mixed with sticky rice as a binder and bamboo poles as reinforcement. Remarkably, the walls are designed to lean in toward the center, acting like a horizontal arch to give it extra strength.
WikipediaAccording to Wikipedia, the design "followed the Chinese dwelling tradition of "closed outside, open inside" concept: an enclosure wall with living quarters around the peripheral and a common courtyard at the center."
The residential units were like townhouses rather than apartments, each with its own stairs. They were also a form of co-housing: "it [has the] unique characteristic as model of community housing for equal. All rooms were built the same size with same grade of material, same exterior decoration, same style of windows, doors, and there was no "penthouse" for "higher echelon", small family owned a vertical set from ground floor to "penthouse" floor, larger family own two or three vertical sets."
They were built to last as well; in 1934 a group of peasants were still able to hold off an attack of modern cannon.
While it was probably a bit noisy in that central communal courtyard, there are some interesting lessons to be learned in how to build secure, dense and communal housing.
Sources: Environmental Graffiti, Wikipedia, Green Homebuilding and Sustainable ArchitectureMore on Co-housing in TreeHuggerGreen Co-Housing Community Development In NubanusitCohousing for Aging Boomers More circular buildings in TreeHugger:A Use For Every Building Dept: Martello TowerMore Rammed Earth in TreeHugger:The Dirt on Rammed EarthNk'Mip Desert Cultural Centre: Rammed Earth Wonder