The archaeological service has recorded 76 ancient towers in Sifnos, more than one tower per square kilometre. Many of them are located in distant places more difficult to reach, but there are quite a few more easily accessible.
During the heyday of the island (around the 6th century BC), and due to the wealth from the ore exploitation, the residents created a network of towers-fryctories in the entire island. Inititally they were close to the mines and later on they extended towards the rest of the island, in cultivable areas, on hilltops and slopes. These fortified and defensive buildings were used as watchtowers and outposts which ensured the communication inside and outside the island, or they used to be the shelters of the farmers in case of pirate raids. The towers were circular. They communicated with each other, as well as with the four ancient acropoles, with mirror or smoke signals.
Aspros Pyrgos (White Tower) in Pantokratoras (6th century BC), Mavros Pyrgos (Black Tower) in Exambela (5th century BC) and Pyrgos (Tower) in Kade (4th century BC) stand out from the towers which are preserved in a fairly long height and they are more easily accessible. Since 2003 dozens of volunteers revive the communication system of fryktories each year on Pentecost Sunday.