The day begins with a drive of about 100km to Tay Ninh to visit the ornate Cao Dai temple. Being the 3rd largest religion in Vietnam, Caodaism blends Buddhism, Catholicism, Taoism, Confucianism, and Islam. There are services held 3 times a day, the most suitable time for visitors to visit is 12 o' clock noon. 
After having lunch at a local restaurant, we proceed to the Cu Chi Tunnel. This underground system was built from 1946 to 1968 by local inhabitants and soldiers using simple tools. During the American bombings, they were turned into an underground city, which could house up to 10,000 people, with trapdoors, living areas, kitchens, storage facilities, armouries, hospitals, and command centres. Visitors can enter some parts of the subterranean tunnels to understand better how the system worked. 
Drive back to Ho Chi Minh City.