The archaeological site at Kato Samiko comprises the prehistoric acropolis at Kleidi and the acropolis of the historical period at Elliniko, east of Kleidi, on the west slopes of Mount Lapitha. The former can be tentatively identified as the Homeric city of Arene and the latter as Samia, Samikon, or Samos.


The rocky hill of Kleidi controlled the north-south maritime and land routes. Cyclopean walls surround the prehistoric acropolis and extend all the way across to the hill opposite, where the Classical acropolis was later established. This second hill was also occupied in prehistoric times by a possible tower or guard-post. Middle and Late Helladic pottery and the remains of a Mycenaean building were identified on the prehistoric acropolis, whereas a tumulus with multiple burials and important finds dating from the Middle Helladic until the Late Mycenaean period was excavated northeast of Kleidi. A large cemetery of the end of the Middle Helladic period, with cist-graves and one tholos tomb, all covered by tumuli, was revealed at the hill's east foot.


The strategically located, naturally fortified hill of Elliniko oversees the only passage from Elis into Messenia and lies close to the low fertile valleys in the north and northeast. The trapezoidal enceinte, which surrounded the hill's highest terraces, is preserved on the east and northeast sides to a height of five to twelve courses. Built of pseudo-polygonal masonry, it had square towers and several large and smaller gates. The enceinte probably dates from the fourth century BC or the Hellenistic period, whereas the smaller inner enclosure probably dates from the sixth century BC. The building stones came from a nearby quarry, east of the city. Within the enceinte are the recently excavated remains of terrace walls and buildings, including a public building with portico, reservoirs, and a group of rooms. A number of cist and tile graves, a Roman bathhouse, and an Early Christian church were investigated to the north and northeast of this acropolis.