The largest towns are Ermoupoli, Ano Syros, and Vari. Ermoupoli is the capital of the island and of the Cyclades. It has always been a significant port town, and during the 19th century it was even more significant than Piraeus. Other villages are Galissas, Foinikas, Pagos, Manna, Kini and Poseidonia.
The history of settlement on Syros goes back at least 5,000 years, to the Early Bronze Age of the Cycladic civilization. This is when the hill-top settlement of Kastri (el; la) began. Archaeologists describe Early Cycladic III (ECIII) culture as Kastri culture.
Kastri, dated by archaeologists to 2800-2300 BC, was one of the earliest settlements in Greece that were protected by stone walls with rounded bastions. Also the cemetery of Chalandriani is associated with Kastri. Inside the fortification, the houses shared party walls and were packed close together. It is estimated that the fortified town was home to up to 300 people.
The site was first discovered and excavated in 1898 by Christos Tsountas, the "father of Cycladic research". Kastri had some of the earliest metalwork in the region, and also some of the earliest use of potter's wheel.