East Attica Starts from Marathon, continues to Nea Makri, Rafina, Porto Rafti, Artemida and Lavrio with its ancient mines. Also east Attica landmarks are really close to Athens airport, so they are suggested for few hours trips. There are quite a few landmarks you can visit, such as:
Amfiareion and Oropos area: A former wealthy attica area, with an archeological site, dedicated to Amfiareion. The site was the central exchange point with Euboea and later destroyed by Christians.
Marathon Tomb: The place where the 192 dead Athenians were buried, after the Marathon Battle of 490 BC.
Marathon Dam: The dam that provided water to Athens. It was built between 1926-1929.
Attica Zoological Park: A place where you can spend time with your family https://www.atticapark.com
Porto Rafti: A place that you can combine a dive at the sea but also seafood, at a local tavern.
Vravrona: a famous archaeological site, as for the temple of Artemis, next to Porto Rafti bay. There is also an archeological museum there, worth visiting.
The place is atmospheric and unique.
Vravrona tower: a medieval tower, left from Athens Latin occupation.
If you want to go southern, here are some nice spots.
Lavrion: ancient mines of silver that funded Athens’ navy are located here. There is also a museum.
Thorikos: another archeological site.
Sounio: the famous Poseidon temple, marks the last point of Attica.