The two Acropolis Museums in Athens are:
(1) The "old" Acropolis Museum, on the temple mount.
(2) The "new" Acropolis Museum which is open for visitors, next to the Saint George Makrygiannis church and the Acropolis Research Center (Κέντρο Μελετών Ακροπόλεως). The "New" Acropolis Museum and the Research Center are at Makrigianni 2-4, Athina 117 42, Greece
Official Web Site Acropolis Museum