National Archaeological Museum
We had to return another day as the museum has very different opening hours. Before going, make sure to check that it will be open. I liked it a great deal, however, if you don't bother with an audio guide or a guide, you may not understand everything. All the explanations of the sculptures, and paintings were in Greek or English. I recommended a visit. It's huge - if you go, go with time to spare because it takes a while to visit - there are endless rooms.