One of the most important archaeological sites of the island, the Mycenaean Acropolis of Agios Andreas, on the eponymous hill (or Ai-Dria as the locals call it) at a distance of 6 km approximately from Apollonia on the way towards Vathi, is one of the most important "witnesses" of the long history of Sifnos.
The archaeological site that was discovered after excavations in 1899 by the archaeologist Christos Tsountas gives important information to visitors about the life and activities of the inhabitants of this settlement during the Mycenaean (13th-16th cent. BC), Geometric and Archaic period.
In an area of ten thousand square meters, visitors will notice a large section of the Mycenaean wall (12th cent. BC) that surrounded the acropolis. Inside the enclosed area, the ruins of five buildings – most likely residential –, the church of Agios Andreas built in 1701, as well as a plethora of mobile findings are preserved.
At the entrance of the archaeological site there is the museum, which exhibits the mobile findings from the excavations.