The authors report a reconstruction of the palaeogeography around the Harappan town of Lothal, major port of the Indus civilisation, using multispectral satellite imagery and environmental analysis. Key results include the identification of a broad tidally influenced palaeochannel adjoining the western part of Lothal and a former estuary towards the east. Micropalaeontological analyses show that Lothal developed over a tidal salt marsh and was subsequently left high and dry as the sea level dropped.