Chinampas are long, rectangular floating gardens that the Aztecs constructed on the shallow lakes of the Valley of Mexico beginning around the 10th to 12th century A.D. Chinampas supplied lakeside cities, such as Tenochtitlan, with over half their total food needs.
Chinampas were made by enclosing rectangles ranging from 8 to 30 feet wide and 100 to 300 feet long with cane, hedges or wattle. The interior was layered with mats, decaying vegetation and lake sediment to form floating islands. Water channels between plots were wide enough so that farmers could pass through in their canoes. The lake water provided abundant moisture for the plants. The rich canal mud kept the soil unusually fertile. A wide variety of crops were grown on chinampas, including beans, maize, tomatoes, chili peppers and squash. Because of the rich soil and easy irrigation, crop yields were extremely high, and farmers managed to attain as many as seven harvests every year.
Although most of the lakes that contained chinampas have been drained and covered by cities, remote sensing techniques have identified sites of ancient chinampas. Additionally, archeologists have excavated sites near lakebeds to study chinampa agriculture, and chinampas are described in early Spanish colonial literature. There are remnants of ancient chinampa canals in lakeside towns, such as Xochimilco in Mexico.