Pueblo Bonito (shown above) in New Mexico, built between A.D. 900 
and 1130, is considered one of the greatest examples of a prehistoric 
apartment building.  The original structure had eight hundred rooms 
and could have accommodated three hundred families.  Walls were 
of stone and adobe, and the ceilings were seven feet high.  Bonito 
was crescent-shaped, enclosing a large open court, and entry to it 
was by ladder.  Because each story was at least one room narrower 
than the one below, terraces in front of each outer row of rooms 
were created.