According to Wikipedia, Saigon Central Post Office (Vietnamese: Bưu điện Trung tâm Sài Gòn) is a Gothic architectural styled post office built between 1886-1891 in the downtown Ho Chi Minh City, near Saigon Notre-Dame Basilica, the city's main church. The building was constructed when Vietnam was part of French Indochina in the early 20th century. Today, the building is a tourist attraction with lots of souvenir stalls inside the post office, although it is still an operating post office in Ho Chi Minh.
We went inside to have a look but as expected it was just another tourist spot with lots of people taking pictures or loitering around. We didn't spend much time there and headed to the Saigon Notre-Dame Basilica Cathedral located right across it.