THE Preservation of Sites and Monuments (PSM), a division under the National Heritage Board, advises the Government on the preservation of sites and buildings of national significance.

National monuments are legally protected by the Preservation of Monuments Act, and all works on them must be approved by PSM.

It is the highest order of preservation status in Singapore.

Besides the architectural merits and historical value of the building, the national significance of the structure is a critical factor in the gazetting of national monuments.

There have been 69 national monuments gazetted since 1973.

They include St Andrew's Cathedral (rebuilt 1856-64), Thian Hock Keng temple (1839-42), Sultan Mosque (rebuilt 1924-28), Raffles Hotel (1887-1907), City Hall (1926-29) and the Cathay Building (1939).

Jurong Town Hall, officially opened in 1975, is the "youngest" on the list.

The second "youngest" national monument is Chung Cheng High School (Main), which was built in 1968.

The oldest building on the list is the former Parliament House and Annex Building, built between 1826 and 1827.