If you are interested in the history of Singapore, and personally the only thing I find interesting about Singapore is its history, this is a good place to visit. Old photographs document the remarkable changes that the island has gone through in the last 40 years. The main exhibit is not very large but there is also a reference library. Unfortunately the reference library was closed for stock taking when I visited so I cannot comment on it.
With the fantastic Singapore History Museum closed for refurbishment and the temporary alternative being very poor the National Archives is probably the best place at present to get a glimpse into Singapore's past.