Architecture, Building and Structure Design Doji Tower Gold and Gem Trading Centre by Nguyen Thi Thu Thuy Hanoi Doji Tower is a gold, gem and jewellery trading centre in central Hanoi. The building combines classical and modern styles in a diamond-shaped form. The base of six floors is tiled with natural marble. The seventh to the sixteenth floors form a large diamond block made of thousands of specially produced glass sheets, which create a distinct light effect. The tower has sixteen floors and three basements, with a total usable area of nearly 19,000 square metres. The first five floors hold a shopping centre for gold, gems and jewellery.