Matsu Tianhou Temple on Nangan honours the sea goddess Mazu, whose name is tied to the islands themselves. It is a compact, active temple rather than a museum piece, with incense, bright paint, and the usual layered offerings of coastal Chinese religion.
The temple is worth visiting early in a trip because it gives cultural balance to all the military tunnels. Matsu is not just bunkers and ferries; it is also a fishing archipelago with older beliefs about the sea.