Indeed the line 1- inaugurated in 1869 (!) - is not the Athens subway (ie.the lines 2&3); it is however a part of the Athens metro system. I would say this is more close to the Athens suburbian railway in a sense that it is not underground.
Το μετρό κατά τη γνώμη μου είναι η πιο εξυπηρετική συγκοινωνία της Αθήνας, καθώς μπορεί κανείς να διανύσει μεγάλες αποστάσεις και να πάει σε πολλές περιοχές σε μικρό χρονικό διάστημα.
Metro doesn't mean underground. There are plenty of overground metro systems worldwide. In fact this is considered one of the oldest metro line in the world. The qualifications for a line to be considered a metro is among others: serving a metropolitan area, electrification, lack of junctions and of course transferring bigger amounts of people than a bus.
