At the South-eastern edge of the plain of Argolid, near the springs of the Erasinos river (nowadays 'Kephalari') and on the main arterial road which in antiquity lead from Argos to Tegea and the rest of Arcadia and Kynouria, there is a small fort at present known as the 'pyramid' of Hellenikon.

According to evidence from the excavations and the typical features of the structure which dates to the end of the 4th century B.C. and not to the prehistoric period, as some scientists have been recently willing to demonstrate. During the later years of Antiquity, the ''Pyramid'' was considered as a burial monument , a ''polyandreion'', while nowadays there is no doubt that it was a fort of the type of small strong-holds which controlled the arterial roads and which are known from other regions of the Argolid.

It has the shape of a tour with its external sides sloping and surrounding a rectangular building of total dimensions 7,03 by 9,07 m. These external walls, which rise with a gradient of 60o up to 3,50 m high become vertical to in order to support the floors of the building. The main entrance of the monument is situated at its eastern side, that is the side which is turned towards the bay of the Argolid. From inside this gate a narrow corridor which leads to a smaller entrance, opened on the southern wall of the main space, a square room with sides about 7 m long.

This impressive monument is built entirely from the gray limestone of the district with large blocks in a trapezoidal and partially polygonal system.

Excavations of the monument whose stone structure had remained stable for 2400 years, were undertaken by Th. Wiegand in 1901, but mostly by L.Lord in 1938. Both published the results of their excavations in specific monographies.