The middle of the third millennium bc sees a new phenomenon – the development of fortified settlements in mainland Greece and the Cyclades. The fortifications at Lerna, barely preserved, are built around 2500 bc; with a rubble foundation and a mudbrick superstructure, they have semi-circular towers protecting access (Figure 7.1) and include rooms covered with tiles or schist slabs. These enclosure walls also exist in central Greece (Wiencke 2000, 649), at Kolonna on Aegina (where they are comparable to those of Troy – AE1, fig. 43) (Aruz 2003, 260–1), and in the Aegean islands, from the northeast Aegean to the Cyclades. At Kastri on Syros the wall blocking access to the site had six horseshoe-shaped towers, which in turn were protected by an outer line of defence (ArchReports 53, 2006–7, 83, fig. 99).