Cao Dai is a funny little religion. It is basically endemic to Vietnam and has two to three million adherents. A sort of mixture of Buddhism and Catholicism!
This is the main temple of the Cao Dai. Pretty impressive. As you may surmise, one has to leave your shoes outside to enter it.
One of their regular prayer services.
A close up of the roof decoration. It is a beautiful structure. We visited it on the way back from the tunnels.