According to Telegraph:

New Acropolis Museum

Inaugurated in June 2009, this light, airy glass-and-concrete building was designed by Swiss architect Bernard Tschumi. Archaic and classical finds from the Acropolis site are displayed here – proud statues of the ancients and life-like stone carvings of animals. The top floor is devoted to the marble frieze that once ran around the top of the Parthenon. About half of the pieces are originals, while the remainder are white plaster copies. The missing pieces were removed by Lord Elgin in 1801 and are now in the British Museum in London. The Greeks have wanted them back for decades, and hope that this blatant presentation will finally convince the British to return them. There’s also an excellent restaurant on the second floor, open till midnight.

Details: theacropolismuseum.gr

Benaki Museum

Housed in a neo-classical building with a lovely roof-terrace cafe, this museum traces Greek art right up the 20th century. Sculpture, ceramics, jewellery, paintings, furniture and costumes are on display, but top pieces include the Thessaly Treasure (a hoard of gold filigree jewellery set with precious stones, dating from the second century BC), two early paintings by El Greco, and the reconstruction of two 18th-century, wood-panelled, Ottoman-inspired living rooms.

Details: benaki.gr