Eleftherios Venizelos, Athens’ modern new airport, is at a distance of approximately 39 kilometers.  The Athens Metro Station is right across the street from the hotel, while the streets around Syntagma are dotted with busses and trolley stops. Limousine service and special taxis can also be arranged upon request at the reception desk.  
From the airport : Exit the airport from the south gate and take Attiki Odos until you meet "Ymittos" ring (exit 16) where you turn left. When reaching Katechaki exit (exit 5), turn right and reach Kareas avenue. Keep on going until you reach the intersection with Mesogheion avenue, where you turn left. At the end of Mesogheion Avenue, you will meet Vassilisis Sofias avenue and turn left. This avenue brings you to Syntagma Square. If you choose to use the Metro, take line 1 until Omonia station, then take line 2 (Sepolia-Dafni) to Syntagma station.