The "green" line with the silver-red trains is almost 100 years old (these particular trains only about 15). The line started operations in 1869 and this station was one of its first. (Click here and go to the photo gallery).
The station is at Plaka. As you can see from the houses up there, it's one of the oldest neighborhoods in Athens and one of the main tourist attractions, very close to Acropolis.
Panoramic view of Monastiraki and Plaka
Where is it on the map?