Since 1902 archaeological investigations at Palaikastro in eastern Crete have sought evidence for two architectural structures: a palace located amongst the substantial remains of Minoan settlement and the temple and sanctuary of Zeus Diktaios referred to by Strabo. In 2001 a geophysical survey was conducted in the Roussolakkos valley to the south-east of the excavated Minoan remains. Previous studies had recorded this as an archaeological ‘nil’ zone owing to the complete absence of cultural surface debris. Seven geophysical zones, covering a total of 20,960 m2, were surveyed using a combination of electrical resistance and magnetometry methods. Anomalies attributed to anthropogenic activity were found in six of these zones. They probably reflect substantial Minoan architecture based on the shape of some anomalies, a comparison with geophysical results from a previously excavated area (Block X) and the occurrence of no pottery later than Minoan on the ground. On this basis the geophysical survey has approximately doubled the known area, of the Minoan settlement. The anomalies may belong to a large urban block though their scale and orientation are also comparable to plans of palatial structures from other sites. Anomalies that could reflect architecture were found in Zone 7, situated in the area of earlier finds of Iron Age votives and Archaic architectural fragments and may therefore be related to the Diktaion.