The biggest part of the altar of 12 Gods is under the metro rails.
Modern and Contemporary era (1821 - )
1891 Discovered.
Ottoman era (1453- 1821)
Byzantine era (331 AC- 1453)
Roman era (30 BC- 330 AC)
Hellenistic era (322- 31 BC)
Classical era (478-323 BC)
Archaic era (800-479 BC)
Constructed in 522-521 BC, by Peisistratus the younger, grandson of the tyrant Peisistratus.
Geometric era (-1100- 800 BC)
Prehistory (-1100 BC)
What I can see
Although there were separate altars dedicated to each god, there was also an altar for the 12 gods, which belonged to the early buildings of the Agora (6th century BC). Apart from worship, it served as a sanctuary for asylum seekers and a starting point for distance measurements. According to a sign, the distance between the altar of the 12 Gods and the port is 45 stadiums, i.e. 9 km. Today, only the southwest corner of the monument is visible.
What I can't see
The biggest part of the monument is under the metro lines. The altar was discovered during constraction of the metro’s superstructure, but the monument was buried until the undergrounding of the metro line. It must be remembered that the aim of archeology is not to expose and exhibit anything discovered, but to develop archaeological and historical research and create a historical record.
Bibliography
Tsogka K., (2012), Αρχαία Αγορά Αθηνών, [Ancient Agora of Athens], Odysseus, Ministry of Culture
http://odysseus.culture.gr/h/3/eh352.jsp?obj_id=2485
Last visit 9/10/2016