Visitors enjoy a performance featuring an ancient Greek organ "hydraulis" played by the Greek organist Ourania Gassiou at the Athens Acropolis Museum in Greece, on March 31, 2018. The summer season of the Athens Acropolis Museum was launched Friday evening with a music concert featuring an ancient Greek organ known as the "hydraulis." At the concert held in the museum's Parthenon Gallery, visitors had the opportunity to enjoy a performance featuring the musical instrument played by the Greek organist Ourania Gassiou, as well as a harp performance. (Xinhua/Lefteris Partsalis)