Delos is one of the smallest islands in the Cyclades. It extends about 5km from north to south and is at no point more than 1300m wide (its surface area is 360 ha). The coastline is mostly steep and offers only a few anchorages. The island barely emerges from the surface of the sea, compared with the prominent landscapes of the other islands in the Aegean Sea.

From north to south, it can be divided into three sections:

• the area of peninsulas and gneiss formations, very exposed to the prevailing winds from the northeast.
• the plain, where the town's religious centre was located.
• the Cynthus massif (113m), continued to the south by that of Kato Vardhia.
   

The climate is semi-arid, with rain in autumn and winter, a very short spring, followed by a long dry season, cooled between July and September by the meltem, a wind from the north. Delos is not lacking in water: it enjoys the benefits of a shallow groundwater table, reached in the town by wells and collected in the countryside simply by digging ditches. The island's inhabitants arranged their soil into farming terraces and created large reservoir basins to catch runoff water, which was used to irrigate some parts of the countryside or for the town's water supply.

Delos is surrounded by several islands and islets that belong to the same archaeological complex as it does. In addition to Mykonos, of which only a part was linked to Delos, there is:

• the two Rhevmatiari islands, opposite the western coastline of Delos. Only the Greater Rhevmatiari, to the south, has yielded archaeological remains.
• Rhenea (today known as 'Great Delos') was an annex of ancient Delos and, in particular, was used as a necropolis. A sanctuary of Artemis and farms administered by the Sanctuary of Apollo were located there. The ancient town of Rhenea was situated in the northwest part of the island.
• Kherroniso, at the southern tip of the island of Delos.
• the Prasonissia islets, off the eastern coast of Delos.
   

Delos and Rhenea

© Efa / F. Ducat