President McAleese visited the Irish pavilion at Expo 2005 in Nagoya yesterday as part of her tour of Japan and South Korea.
The Expo is a cultural showcase for 122 nations, which is expected to draw more than 15 million people over the coming months.
The centrepiece of the Irish exhibition, which is built around a Celtic art theme, is a selection of six replicas of high crosses on loan from the National Museum of Ireland.
It also includes replicas of the Book of Kells and samples of contemporary literature and rock music.
Mrs McAleese said: "I've no doubt this is going to be a huge success. Nothing will be bigger in the world this year. What better way for Ireland to present itself to Japan and the world."
Each country at the Expo will be the focus of a national day, with Ireland's turn falling on March 31st.
The President said the Expo's eco-friendly themes were a "timely call because we are increasingly coming to accept that the problems of unsustainable living can no longer be overlooked."
The President met Emperor Akihito yesterday at the Imperial Palace. Empress Michiko did not attend because of illness.
In the evening the President hosted a St Patrick's Day party in the Okura Hotel in Kyoto, with the group Altan.