Oita "Big Eye" Stadium
Oita City, Oita Prefecture, Japan
KT Group

This spherical orb appears to view the world around it

© Koji Kobayashi

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As the centerpiece of the facilities in Oita Sports Park, Big Eye is a multipurpose stadium with a retractable roof, built for the World Cup soccer tournament this year, the National Sports Festival in 2008, as well as various sports, concerts, and other entertainment venues. It has a unique shape, with part of the spherical surface appearing on the ground. This simple geometric shape blends in with the natural environment of the green foothills that extend from the surrounding Takaoyama Park.

The roof has a two-layer spherical surface, consisting of a lower layer, which is a three-dimensional arch-framed, fixed, bone-like structure; and an upper layer, which is a two-piece, semi-lunar-shaped retractable membrane roof. The roof maintains its spherical shape when fully opened, while being retracted, and when fully closed, and is the largest of its type in the world used for a large space structure. The outer layer slides to close over the fixed inner roof in about 20 minutes, just like eyelids moving along the curve of one’s eyes, hence the name "big eye."

The retractable roof utilizes a teflon membrane that is translucent, maintaining sufficient light on the field even when it is cloudy or the roof is closed. With no requirement for artificial lighting during the day, low energy costs are achieved. Furthermore, slits have been designed between the roof and the seats allowing ventilation and viewing of the surrounding scenery for spectators.

The stadium arena was designed with athletic competition tracks, but during a soccer match, 9,000 retractable seats cover this area, enabling easy viewing, and a feeling of being right next to the field. An underheating system is used for the natural turf of the soccer pitch. A traveling camera is installed in the arch frame of the roof, which can capture rare views during competitions.

Formal name of Project:
Oita "Big Eye" Stadium, of Oita Sports Park

Location:
Oita City, Oita Prefecture, Japan

Gross square footage:
1,000,000 sq ft

Client:
Oita Prefecture

Architect:
KT Group:
Kisho Kurokawa Architect & Associates, Takenaka Corporation,
SATO BENEC, Takayama Sogo Kogyo Co.,Ltd.