National Diet Building

The National Diet Building is the facility that houses the Diet, the center of Japan’s national government, and is located in Nagatacho, Chiyoda Ward, Tokyo. It is about a three-minute walk from Kokkai-gijidomae Station on the Tokyo Metro, and serves as the place where the bicameral Diet, consisting of the House of Representatives and the House of Councillors, carries out its work. Important matters of national governance, such as enactment of laws, approval of the budget, and designation of the Prime Minister, are deliberated here.

History and Background of Construction
The first Imperial Diet was convened in 1890, and the first temporary Diet building at the time was destroyed by fire just two months later. The second temporary Diet building, constructed afterward, was also destroyed by fire, and a third temporary Diet building was then built.

Construction of the current National Diet Building began based on a plan selected through a public competition held in 1920, with detailed design work carried out by Fukuzo Watanabe and other engineers from the Ministry of Interior. However, the work was temporarily suspended due in part to responses to the burning of the temporary Diet buildings, and the building was finally completed in 1936, 17 years after construction began.

Overview of the Building
The National Diet Building is a steel-framed reinforced concrete structure with three stories above ground (the central tower has four stories) and one basement level. The building measures approximately 206 meters in length and about 89 meters in depth, and the central tower reaches a height of about 65 meters. Approximately 30,000 tons of granite and marble from all over Japan were used in its construction, and a total of 2.54 million workers are said to have been involved.

The building is symmetrically designed, with the House of Representatives on the left and the House of Councillors on the right when viewed from the front.

Visiting the Building
The National Diet Building can be toured by advance reservation. Both the House of Representatives and the House of Councillors can be visited free of charge, and the tour takes about one hour. Visitors are guided by staff along a designated course.

House of Councillors Tour
- Visitor Lobby (displays include a replica of the Speaker’s gavel and the Emperor’s chair)
- Plenary Chamber
- Imperial Rest Room
- Central Hall
- Forecourt

House of Representatives Tour
- Plenary Chamber
- Imperial Rest Room
- Noblemen’s Room
- Central Hall
- Forecourt

There is also a shop selling original goods such as sweets exclusive to the National Diet Building and clear files featuring illustrations of successive prime ministers.

Central Hall and Architectural Beauty
The Central Hall is located directly beneath the highest central tower of the Diet Building, and its ceiling is about 33 meters high. It houses bronze statues of Itagaki Taisuke, a pioneer of the freedom and civil rights movement; Okuma Shigenobu, founder of Waseda University and former Prime Minister; and Ito Hirobumi, Japan’s first Prime Minister. The fourth pedestal, which still has no statue, is said to symbolize the idea that politics is never complete, and it is associated with many anecdotes.

The floor of the hall is decorated with about one million mosaic pieces, using more than a dozen types of marble. Coral limestone from Okinawa is used for the columns and walls, and shell fossils can be seen in the material. Oil paintings depicting Japan’s four seasons are displayed in the four corners.

Splendid Decoration of the Imperial Rest Room
The “Imperial Rest Room,” where the Emperor rests during the opening ceremony, is the most luxurious room in the National Diet Building. Its interior incorporates the finest elements of traditional Japanese craftsmanship, including Japanese cypress, lacquer, gold leaf, and raden (a decorative technique using shell inlay). It is said that Mount Fuji could once be seen from this room, but it can no longer be seen because of surrounding buildings.

Structure of the Chamber
The plenary chamber where sessions are held is on the second floor and features a double-height open space. The ceiling has a stained-glass skylight adorned with beautiful arabesque patterns. The seats are arranged in a semicircle, and the House of Representatives plenary chamber has 460 seats. This is more than the current number of members, reflecting a design that anticipated future expansion.

Careful attention has also been paid to acoustics, with extensive use of wood and silk fabric to reduce reverberation.

Forecourt and Illumination
In the forecourt of the National Diet Building, the “trees of the prefectures,” donated from across Japan to commemorate the 80th anniversary of the opening of the Diet in 1970, are planted. A fountain was also installed in 1990 to commemorate the 100th anniversary of the opening of the Diet.

In mid-November, the approximately 300-meter-long ginkgo avenue in front of the building turns golden, making it a beautiful autumn foliage spot known as the “Golden Road.”

In addition, to commemorate the 100th anniversary of the opening of the Diet, the central tower has been illuminated from sunset until 8:00 p.m. during regular Diet sessions since November 1990, giving the National Diet Building at night an enchanting atmosphere.