A severe incongruity has long existed between the well-known complexity of ancient Maya civilization and the relatively feeble economic base that could be reconstructed for it. Recent fieldwork has ihdicated that much more intensive cultivation patterns were used than was previously thought. Data from the use of synthetic aperture radar in aerial surveys of the southern Maya lowlands suggest that large areas were drained by ancient canals that may have been used for intensive cultivation. Ground checks in several limited areas have confirmed the existence of canals, and excavations and ground surveys have provided valuable comparative information. Taken together, the new data suggest that Late Class period Maya civilization was firmly grounded in large-scale and intensive cultivation of swampy zones.