We find Tilos in the southeastern Aegean Sea, situated between Nisyros and Halki. It is one of the smallest clusters of islands that is 209 sea miles from Piraeus and 48 miles from Rhodos. We meet Nisyros at a distance of 13 km, Halki in 18 km, Simi in 34 km and the Near East peninsula of Knidos in 20 km. The little island Antitilos is situated just 2 miles from Tilos. Within a longer or shorter distance from Tilos coasts, 16 small islands and rocky islets are situated. Its entire size is 63 km2 and its coastal length is 63 km.
Its terrain is – basically – rocky, semi-mountainous and mountainous and Ai-Lias is its highest mountain top (612 m). The small fertile valley of Eristos in the middle of the island that comes down to the beautiful beach of Eristos constitutes an exception in Tilos. In Megalo Horio, the soil is more or less fertile, because of the number of springs with good water quality that traverse underground. Many gulf formations, caves and beautiful beaches complete the variety of the island morphological formation.