Hadrian's Arch - so easy, one of the most famous & recognizable monuments in the very heart of Athens historical centre.
1) From Syntagma Sq: Walk five minutes straight down Amalias Ave. on the Greek Parliament side, passing Athens National Gardens.
2) By Metro: Take red line, get off at ACROPOLIS STATION. Exit the station on MAKRYGIANNI STREET. At the top of the stairs walk straight forward to Dionysiou Areopagitou street, turn right and after 20 meters (2-minute walk) you will be on a main street Amalias Ave. Across the street is The Temple of Olympian Zeus and to the left is Hadrian's Arch.