The cities of Athens and Thessaloniki celebrate the memory of Maria Callas today, 25 years after the greatest opera diva died alone in Paris. As part of the Athens Festival and weather permitting, the Athenaeum International Arts Center is organizing an ambitious concert at the Herod Atticus Theater, in Athens, while the Thessaloniki Concert Hall is offering an opera gala on its premises. In Athens, «Dies Irae – Sacrae Ariae» will feature works by Bach, Mozart and Verdi, interpreted by soprano Irene Tsirakidou, mezzo-soprano Markella Hatziano, tenor Cesar Gutierrez and bass Dimitris Kavrakos. The soloists will be accompanied by the Prague Philharmonic Choir as well as the newly established Symphony Orchestra of the Balkans – which includes musicians from Albania, Bulgaria, Greece, Croatia, Romania, Slovenia and Turkey, among other countries – and which will make its debut appearance at the Herod Atticus under the direction of Louli Psychouli, the Athenaeum’s director. The event is being sponsored by HSBC bank. In Thessaloniki In Thessaloniki, the Callas tribute will feature various arias from operas by Bellini, Verdi, Puccini and Donizetti, interpreted by soprano Dimitra Theodosiou. The soprano will be accompanied by the Thessaloniki State Orchestra under the direction of Nikos Athinaios. Besides tonight’s gala performance, the Thessaloniki Concert Hall is also hosting a unique exhibition of Callas memorabilia. All that is going on display tonight belongs to Carlo Tanzi, a passionate collector who has spent the last 47 years gathering all sorts of items related to the celebrated diva. Tanzi, who curated the exhibition, is presenting 350 previously unpublished photos of Callas, among other items. Beyond tonight’s event, Callas fever will continue as celebrated Italian filmmaker Franco Zeffirelli, a friend of Callas’s, is scheduled to visit Athens at the end of this month in order to present his latest film «Callas Forever.» The film stars Fanny Ardant, Jeremy Irons, Joan Plowright and Angela Molina. «Dies Irae – Sacrae Ariae» at the Herod Atticus Theater, Dionysiou Areopagitou, tel 010.323.2771. Ticket purchases at the festival’s box office, 39 Panepistimiou, tel 010.322.1459. Opera Gala – Maria Callas Memoriam at the Thessaloniki Concert Hall, 25 Martiou & Paralia, tel 0310.895.800, 0310.895.938-9.