Grammatiko is situated in the hills of the northeastern part of the Attica peninsula, 6 km from the South Euboean Gulf coast, at about 210 m elevation. It is 4 km southeast of Varnavas, 5 km north of Marathon and 32 km northeast of Athens city centre. The municipal unit Grammatiko consists of the villages Grammatiko, Agia Marina and Sesi. It has an area of 51.674 km2.[5]