Offering visitors the unique opportunity to combine a nocturnal visit to Greece’s best-known ancient ruins with musical entertainment under the September full moon, the Culture Ministry is organizing free concerts tomorrow night in archaeological sites and museums all over the country. Fifty-five sites, including the Acropolis and the Roman Agora in Athens, Delphi, Vergina, Delos and ancient Corinth, will be open from 9 p.m. to 1 a.m. on Monday, free of charge, in what the ministry has billed as a farewell to the last full moon of the summer. Singers and musicians including Maria Farantouri, Maria Dimitriadi, Antonis Kaloyiannis, Nena Venetsanou, Savvina Yiannatou and Sotiria Leonardou will perform at 48 of the sites. Some concerts will be held in museum courtyards. The Acropolis, Sounion, Olympia, Poliochni on Lemnos, Abdera in Thrace, Stageira in Halkidiki and Aphaia on Aegina will be open but without music.