In this article, three late medieval fortifications are examined, which once formed a maritime defense system along the northwestern coasts of Asia Minor in present day Turkey, roughly opposite Lesbos. These buildings are: the Tower of Büyük Maden Island in Ayvalık, the Tower of Mardaliç Island in Dikili, and the Castle of Çandarlı, which are located between the Gulf of Edremit and the Gulf of Çandarlı. Although this area hosts several renowned ancient cities of Asia Minor, there is insufficient literature on late medieval historical topography studies and architectural history from an interdisciplinary perspective. The fortifications in question were previously subject to only some superficial analyses and were considered separately, without a territorial understanding. The methodological background of this new research lies in architectural history and landscape archaeology. In this case, material characteristics were examined through field surveys and were dated through analogies with nearby examples. Meanwhile, primary sources like contemporary chronicles and textual and cartographic portolans were considered in order to examine the historical topography of the region. A preliminary viewshed experiment tried to clarify the curious positions of the towers on lower hills of their islands, in the light of a long range watchtower function that is directed towards the open sea.