Obama was dressed casually in khaki pants and a windbreaker as he walked with a guide around the Acropolis.
Later on Wednesday, he was expected address Greece's debt issue. The trip to Europe is his last while in office. Obama is visiting Greece, Germany and Peru on his last trip abroad as president.
He is expected to meet German Chancellor Angela Merkel and other European leaders in Germany and Greece. In Peru he will see Chinese President Xi Jinping and other Pacific leaders at an economic summit.
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