One of the best museums to see in Athens from paintings, mementos, traditional Greek dresses, religious artifacts and icons, ancient tools, jewelries, musical instruments and some modern art. Be aware that some rooms are part of their temporary exhibit that requires additional entrance fee. Worth a visit and a good glimpse of Greek culture.

I wasn't expecting much, but this museum is a really enjoyable escape from the rest of Athens. It's air conditioned, and admission is free for those under 18. The exhibits are surprisingly interesting if you take the time to read some descriptions. The museum isn't too big, but the architecture is nice, and it's a good way to spend a couple hours away from the heat. Currently, the restaurant and third floor are under construction.

If you are staying longer in Athens, than this is worth doing. I would not priorities it given there are so many nicer and more interesting things to to do. The collection is mostly made off orthodox art, jewelry and clothing. The most interesting things are probably the very old figurines and pots on the ground floor. You definitely don’t need two days and can be all done in a couple of hours.