The museum will have a permanent 2,800 m² gallery space at the new glass clad building within a glass rotunda known as the Singapore History Gallery. It will feature the history of Singapore from the 14th century in a story-telling approach. Images and film can be projected on its 15-metre high cylindrical walls. There will be a narration of the history and display of artistic expressions of the history. Other permanent exhibitions include the Singapore Living Galleries which will feature exhibits of photography, cuisine, film, fashion and other lifestyle artifacts.
A ramp spiral in the new building leads down to an exhibition space holding the nation's treasures which includes the Singapore Stone and 14th century gold ornaments unearthed from nearby Fort Canning Hill in 1928. There will be a 250-seat auditorium known as The Mesh for talks, lectures and workshops for the young and old at the Fort Canning entrance. It will have retail facilities as well as a cafe and a restaurant at the Stamford Road block of the building. Elevators and escalators have been constructed to facilitate the disabled to have access to the museum. An area will feature classrooms and outreach programmes. A vehicular entrance can be accessed by Fort Canning Road at the new building. In the basement, there is a column-free 1,200 m² exhibition gallery for temporary exhibits. It has insulated walls without windows and the space is climatically controlled to protect the exhibits from light and heat or humidity changes.
A resource centre will be housed in the building which will contain old books, photographs, negatives and stamps for public viewing. National Museum introduced a new wireless technology which allow automatic playing of audio and visual material when visitors enter designated zones. The museum has held several temporary exhibitions before its official opening which include a film festival and a men's fashion show, during which the main foyer will feature nude male mannequins.
National Museum was designed in Neo-Palladian and Renaissance style and consists of two rectangular parallel blocks, with a dome at the front of the building. Its architects were Henry McCallum who designed the original version and J.F. McNair who designed the scaled down version of the building. The building has two rotundas, a new glass-clad rotunda at the rear area of the building. Its glass rotunda is a cylindrical shaped building which is made up of two drums, with the outer one made of glass which sheathes an inner one made of wire mesh. Black out curtains has the same length of the inner drum with images projected on sixteen projectors in the day. The curtains are drawn after sunset, and projection can be beamed out through the glass to get a view of the city. Coats of arms are found on the building's front.
The redeveloped building was designed by local W Architects with the glass-clad rotunda designed inspired by Chinese American I.M. Pei. The chief design consultant was Mok Wei Wei from W Architects, who was appointed in June 2004 and modified the designs of the glass rotunda and the atrium between the two buildings. The new glass clad building was designed such that the old building would still be the centrepiece of the museum. A six-metre gap exists between the back of the main museum building and its new annexe as conservation guidelines do not allow old and new buildings to be directly connected. In the gallery theatre, bricks are designed in a herringbone brick pattern, which helps to control the echoes and acoustics in the space. Initially, the designers planned to use bricks from the old National Library building, but the cost was too expensive. Black concrete flooring was used for the new block instead of gray granite flooring as initially planned.