This preserved wartime tunnel in Barangay Santo Tomas was built during the Japanese occupation of the Philippines and later opened as a local historical site. The known passage is short, about 40 metres, but it gives Ilagan a concrete link to the war years rather than another roadside monument.
Visit it for the atmosphere and the story, not for scale. It pairs easily with the city centre sights and makes sense as a brief stop on the way to or from Ilagan Sanctuary.