The Ancient Towers of Sifnos, in the Cyclades: In the year 524 BC, Sifnos was attacked by the Samians after they refused to give them money. The Samians ravaged the island, killing many and leaving it completely destroyed. It is believed that the towers of Sifnos were built following the invasion of the Samians in order to defend it and be prepared in the case of future attacks.
A complex network of watchtowers was therefore built in order to set up a system of communication whereby the Islanders could be warned in time in case of a sea invasion, especially by pirates. These towers were tall, round and strategically placed across various locations on the island. If there was an attack, a large fire would be lit on the nearest tower's roof. This would then be seen by the closest tower where the next fire would be lit. The next tower would follow and thus a chain reaction of sorts would be set up to protect the Islanders.
While most of them were used as watchtowers, some were also used as protective buildings for the women and children and were filled with agricultural equipment, storehouses, and reservoirs. About fifty-seven of these ancient towers are located all over the island. All of them were built between the 6th and 3rd century BC as is shown by their size and method of building. The towers had two floors with internal walls that separated them. Sadly, most of them are ruined.
The most famous tower of Sifnos is located on the northeastern side of the island. This tower, called Aspros Pyrgos (White Tower) dates back to the Roman era and is one of the few that is still in good condition. Other towers in good condition are the Black Tower in Exambella village and the Tower of Katavati, on the way to Vathi.