The Mycenaean Tholos Tomb at the site “Haratsari” near the modern village “Koryphasio” (formerly called Osmanaga) was found looted and excavated by Konstantinos Kourouniotis in 1926. It is one of the oldest tholos tombs in mainland Greece. It was constructed according to corbelling technique with small rough flat stones. The diameter of the burial chamber is about 6 m. and the entrance was blocked with small built stones and covered by three large rough stone lintels. Inside the chamber there was a fire layer.

Few bone fragments were found, as well as pottery sherds, from which a few vessels were reconstructed, mostly dating to the late Middle Helladic and Early Mycenaean period (17th century BC) and showing clear Minoan influences. Traces of luxury objects, such as silver utensils and an Egyptian porcelain pyxis, were also found. The finds from the Tholos Tomb of Koryphasio are now kept in the National Archaeological Museum.