Attention has been called in recent years to the existence of extensive tracts of pre-Columbian ridged fields and planting beds in the seasonally flooded lowlands of eastern Bolivia (Denevan 1963, 1966; Plafker 1963) and northern Colombia (Parsons and Bowen 1966). In the summer of 1965, while on a commercial flight approaching the airport at Guayaquil, Ecuador, I observed and photographed raised platforms and ridges in the Rio Guayas floodplain that were strikingly similar to the Colombian old fields that I had only recently been mapping. Further investigation, both on the ground and in a low-flying reconnaissance aircraft, established at least two concentrations of these vestiges of an ancient, laborintensive, agricultural system. In one, on the low-lying land immediately across the Rio Guayas from the airport, long parallel systems of ridges and furrows predominate, while more or less rectangular planting platforms are characteristic (Fig. 15.1) of the other, which is under the flight path of approaching aircraft some 14 to 16 kilometers to the northeast of the airport, near the head of Estero El Rosario, a right bank tributary of the Rio Babahoyo.