The Luna Watchtower is the most famous of the 5 watchtowers in La Union. The other watchtowers, built in the years after 1572, can be found in Balaoan, Bacnotan, San Juan, and in the capital city of San Fernando. It is known for its distinctive two-toned colors as a result of rehabilitation. A storm destroyed the leaning half of the structure, prompting the local government, through funding assistance from the National Museum, to rebuild it in 2017.
Watchtowers in the preHispanic Philippines were crucial to the security of towns in the country. Mostly made of coral blocks held together by lime and egg whites, they served as the first line of defense; “symbols of security to the townspeople who were vulnerable to the marauding, predatory pirates.” According to stories passed on by elderly residents in La Union province, a sentry manning a watchtower is tasked to catch the sight of a suspicious-looking seacraft manned by Moro or Chinese pirates in the vast sea moving toward the shore. As a sign of impending danger, the anxious sentry would raise the alarm. Church bells would then ring to warn the townspeople of the imminent danger. It served as a sign for them to run and seek shelter behind the thick walls and barred doors of the town church.