Central museums in Syntagma
Athens is an 100% destination for museums. There are museums showing prehistoric periods of Greek culture and civilization, with Neolithic artefacts, museum showing classical history of Athens and Greece, Byzantine and medieval history museums, but also modern ones, with collections, most of the times also private ones.
Greece is full of museums and archeological sites, and there are also Orthodox churches you can visit.
Nicholas P. Goulandris Foundation – Museum of Cycladic Art, founded in 1986, hosting amazing collections of Cycladic and Cypriot art. Neofytou Doyka 4, Syntagma metro, +302107228321 http://www.cycladic.gr
Numismatic Museum, Panepistimiou 12, +302103643774 http://www.nummus.gr
Benaki museum (Main building) Koumpari 1 & Vas. Sofias (Syntagma metro) +302103671000, https://www.benaki.gr/index.php?lang=en
Museum of the city of Athens, Paparrigopoulou 5-7, +302103246164 http://www.athenscitymuseum.gr/
Byzantine Museum, Vas. Sofias 22, Evaggelismos metro +302107211027 http://www.byzantinemuseum.gr/en/
War Museum, Rizari 2, +302107252974 http://warmuseum.gr/
Jewish museum of Athens, Nikis 39, +302103225582 https://www.jewishmuseum.gr/
Athinais Contemporary Art museum, Kastorias, 34-36 – Votanikos, +302103480000 http://www.athinais.com.gr/el/
Theocharakis Foundation 9, Vas. Sofias Avenue & 1, Merlin Str. Athens +302103611206 http://thf.gr/en/home/
National Museum of Contemporary Art, Kallirrois Avenue & Amvr. Frantzi Str, Athens, (Syggrou-Fix metro) +302111019000 http://www.emst.gr/en
If you want to learn more thing about Athens museums, here is the full museum list If you would like to visit Galleries around Plaka or Athens, it is a must experience as well.