I'm going to have a free day in Athens between two trips -- I should arrive there some time Saturday, and then leave on Sunday afternoon.
However, I've been warned that many tourist attractions such as the Acropolis might be closed on Sunday -- is it true? I can't easily find an official source online, and I am afraid that the opening times might have changed.
Official hours are available from the Ministry of Culture website, and all the locations I checked meshed with hours posted on independent websites.
The major monuments, museums, and archeological sites in Athens are open on Sundays, even in winter, for example
Smaller museums close on Mondays, especially in the off-season, as is common in Western countries. They will also close on more public holidays.
The ministry website is incomplete; for example, it lists no hours for the Theatre of Dionysus Eluthereos or for the Temple of Hephaestus. You will need to rely on other sources, as with monasteries and other private attractions which set their own hours for when visitors are permitted.
