With the start of the 2025 World Exposition in Osaka, western Japan, just over a year away, organizers say one of the event's centerpieces is nearing completion.

The media was invited to see the 80-percent-finished Grand Roof, also known as the Ring.

When complete, it will be one of the world's largest wooden structures, with a circumference of 2 kilometers and a height of up to 20 meters. An 8-meter walkway on top will offer visitors a unique vantage point.

Critics say the Ring's construction cost of 34.4 billion yen, or nearly 230 million dollars, is unacceptably high.

Questions have also been raised over how the building will be used afterwards.

The Expo is scheduled to open on April 13th next year.