The old City Hall building - now part of the National Gallery Singapore - has been the backdrop to some key moments in Singapore's history since 1929.

A multimedia exhibition aims to shed light on the monumental structure's transformations over the years - from its original function as the Municipal Building to housing the world's largest public collection of Singapore and South-east Asian modern art.

City Hall: If Walls Could Talk opens at the gallery on Sunday and will run for two years in the City Hall Chamber on its third floor.

The main part of the exhibition is a 20-minute-long multimedia show introducing visitors to the history of the space with the help of sound effects, video projections and an interactive screen.

The former City Hall building was not always known by that name.

It was the island's Municipal Building when it opened in 1929 and was later renamed City Hall in 1951, when King George VI gave Singapore city status.

It was occupied by the Japanese authorities during World War II, who later held their surrender ceremony there in 1945.

Founding prime minister Lee Kuan Yew and his eight Cabinet ministers were sworn in at City Hall in 1959, forming the first fully elected government of Singapore.

It was on the steps of the same building that Mr Lee recited the Proclamation of Malaysia on Sept 16, 1963, declaring the formation of the Federation of Malaysia with Singapore as a member state and signifying the end of British colonial rule on the island.

City Hall housed various government offices after Singapore became a sovereign state on Aug 9, 1965.

Today, the former City Hall and Supreme Court buildings form the National Gallery Singapore, which opened in 2015.

The exhibition culminates in a Social Wall, a large interactive screen on the third floor.

It invites visitors to look at images of artworks from the National Collection and think about the contexts in which they were created.

Retired arts manager Juliana Lim, 69, worked in the City Hall building twice - in the mid-1970s, for the Ministry of Communications, and in the early 1980s, with the Ministry of Culture.

The building, she recalls, may have been grand, but was "humble, almost grimy" on the inside, she says, adding that the gallery's present-day Padang Atrium used to be an open-air yard where cars were parked.

City Hall was a place where important decisions were made, giving her a front-row seat to changes such as the launch of the Area Licensing Scheme - a forerunner of the Electronic Road Pricing system - and the Ministry of Culture's efforts to make the Singapore Festival of Arts more international.

Ms Suenne Megan Tan, the gallery's director (audience development & engagement), says: "As a museum for the people, we wanted to create this exhibition so that City Hall can continue to be a place where important memories can be shared, and to which future generations of Singaporeans can return to learn and experience the connection between history and art."

Other related exhibitions at the gallery include Listening To Architecture: The Gallery's Histories and Transformations, and Memories Of City Hall.

The latter, a small showcase on display at the Singapore Courtyard till Dec 29, sheds light on the memories of people based in the City Hall building from the 1960s to 1980s.