There are a wealth of beautiful old colonial-era buildings in Saigon. Unfortunately, many are falling into a state of neglect and disrepair. Worse, some are being knocked down to make way for bland modernity.
Here's a pic of what looks like a magnificent old estate at the corner of Vo Van Tan (formerly Tran Qui Cap) and Ba Huyen Thanh Quan in District 3. It's surrounded by dreck skirting it like an apron -- tin roof eateries and various flotsam and jetsam. Whatever it is, it's an historic treasure.
I think one reason that you never hear about architectural masterpieces like this is because the period pre-1975 is a touchy issue. Few people like to talk about history. My sense is most would rather leave it alone -- no sense in inviting trouble. This collective amnesia sometimes reminds me of the "memory holes" in the novel "1984" by George Orwell.