Marinatos began his career in Crete as director of the Heraklion Museum along with Georgia Andrea in 1929 where he met Sir Arthur Evans. He conducted several excavations on Crete at Dreros, Arkalochori, Vathypetro and Gazi, all of which resulted in spectacular finds. In 1937, he became director of the Antiquities service in Greece for the first time. Shortly afterwards, he became professor at the University of Athens. He turned his attention to the Mycenaeans next, regarding them as the first Greeks. He excavated many Mycenaean sites in the Peloponnese, including an unplundered royal tomb at Routsi, near Pylos. He also dug at Thermopylae and Marathon uncovering the sites where the famous battles had occurred.