Sangoro Iwanaga mastered the dry masonry technique from Satsuma masonry, and built the wall stones of the Gosekkyo bridges. Sangoro Iwanaga built Gosekkyo bridges by changing Bizen style of packing chestnut stones inside the wall stones to a method of packing huge stones densely inside the wall stones. Sangoro Iwanaga built the Gosekkyo bridges using a method of packing huge stones inside the wall stones, which eliminated mechanical effect of the fan masonry method brought from Higo. The fan masonry technique developed in Higo and the Makidomo stone wall technique learned from Bizen stonemasons were utilized in the reaction stones.
