The princess looked around the Expo site from the Grand Ring, an elevated pedestrian walkway that is the largest wooden structure in the world.
After being told that materials used for the Grand Ring were produced in Namie, a town in Fukushima Prefecture hit hard by a massive earthquake and tsunami in 2011, she said, "This is very good for reconstruction."
Princess Aiko also visited the International Red Cross and Red Crescent Movement Pavilion run by the Japanese Red Cross Society, which she works for. She watched a video explaining about Red Cross staff's activity in areas affected by natural disasters and conflicts.
At the Japan Pavilion, run by the Japanese government, Princess Aiko said that she was struck by the huge potential of algae and microorganisms.
On Friday, the princess will visit the Singapore Pavilion and Earth Mart, a food-themed pavilion.
[Copyright The Jiji Press, Ltd.]