The primacy of the island world can be established by an examination of the phenomenon of peraiai, that is, the control of pieces of land on the mainland by island poleis. Peraiai is only one side of island-mainland relations. This chapter initially examines the case of Miletus and her control over neighbouring islands (e.g., Leros, Tragia, etc.). The main focus is on island peraiai. It examines all Aegean islands known to have owned a peraiai: Thasos, Samothrace, Tenedos, Mytilene on Lesbos, Chios, Samos, and famously Rhodes. It emphasizes the degree of diversity in the forms of control exercised over the peraiai and highlights the necessity of frequent interaction for maintaining such a control. Peraiai may have been the extension of an island onto the mainland, but at the same time, they were different, often marginal locations. The position of exiles on the peraiai exemplifies their ambivalent position as close, yet marginal, for the insular geography of the Aegean.