There are 18 study models on show, illustrating the thinking process of another critical feature of Reichstag's design, the huge glass dome erected on the curve roof.
"The symbol of the unified Germany, which the Reichstag represented, was rarely reflected in the dome that sits on top of the building. On show are some of the study models we made at the time, exploring different options we conceived for the dome," De Grey explains.
"We felt it was inappropriate to rebuild the original historic dome, but equally, that it was an opportunity to create a contemporary symbol for the people of Germany."
The glass dome offers a great 360-degree view of the surrounding Berlin cityscape and has since helped the Reichstag to become a popular tourist attraction.