In 1876 the archaeologist Heinrich Schliemann discovered in Mycenae six graves , which he believed were those of kings and ancient Greek heroesâ '' Agamemnon , Cassandra , Evrimdon and others . In 1876 the archaeologist Heinrich Schliemann discovered in Mycenae six graves , which he was confident belonged to kings and ancient Greek heroesâ '' Agamemnon , Cassandra , Evrimdon and their associates .