Chinampas are narrow, rectangular beds or platforms about 2-4 meters wide and 20-40 meters long, which are constructed by alternating layers of lake mud and thick mats of decaying vegetation over shallow lake bottoms or in marshy zones.
Below is an illustration of Aztecs building a chinampa, in which they will farm and tend different crops
Van Tuerenhout (2005)
Sanders et al. (1979)