In a joint project started in 2018, Ghent and Utrecht Universities investigate the fortifications of Thorikos, mentioned in ancient and early modern sources. In his account of the Peloponnesian War, Xenophon (Hellenica I, 2, 1) related that the Athenians fortified Thorikos in the first year of the 93rd Olympiad (408/407 BC). This remark most likely refers to the maritime fortress on the Aghios Nikolaos peninsula, but other defensive structures are not to be excluded. In particular, the fortifications observed by both the American traveler Edward Dodwell in 1801 and the British colonel William Martin Leake in 1841 come to mind. These were described as walls with square, projecting towers surrounding the town with a circuit of over 4.5 km.
Little appears to remain of these walls today, and it is possible that they were demolished for building material during later infrastructural works related to modern mining activities. But a stretch of a 0.80 m thick, double-faced wall with large boulders discovered in the western part of the site may be connected with the historical observations. To the south and southwest, ancient Thorikos would have been protected by an estuary in the now silted-up Adami plain and lower Potami valley, so a start of these fortifications in the southwest is plausible. Recent excavations focus upon a possible tower or northern gate in the prolongation of this wall, between the West Necropolis and the Industrial Quarter. Associated pottery suggests a date in the late 5th century BC.