Picture taken on May 23, 2018 shows a man visiting the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities. (Photos: Xinhua)

Picture taken on May 23, 2018 shows a gold leaf crown exhibited at the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows the detail of wooden funerary model of a ship displayed at the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows the gold death-mask known as "mask of Agamemnon" exhibited at the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows a visitor taking photos of a marble statue at the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows the columns of the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows the building of the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.

Picture taken on May 23, 2018 shows ancient jewels displayed at the National Archaeological Museum in Athens, Greece. Located in the center of Athens, the National Archaeological Museum houses more than 20,000 exhibits, including the world's finest collection of Greek antiquities.