The 1891 Gustave Eiffel–era building is still a working post office. Inside: vaulted ceilings, mosaic floors, and an enormous Hồ Chí Minh portrait.
Buy a postcard and send it from inside — the stamps are beautiful. Old Saigon postcards from the gift counter make great souvenirs.
Notre Dame Basilica across the street is currently under restoration (2018–ongoing). You can still photograph the exterior.