In my travel guide book, the Saigon Zoo and Botanical Gardens is recommended for a visit. Within that area you can also visit the Museum of Vietnamese History and Den Hung Temple.
The botanical garden has tropical plants most of which can also be found in the Philippines. The Vietnamese are creative in making the place colorful and interesting by planting various flowering plants arranged artistically and employing various gardening techniques.
Below are the pictures of what Saigon Botanical Gardens have to offer.