The border between the United States and Canada blurs a bit between Blaine, Wash., and Surrey, B.C. There stands the Peace Arch, a 20-meter monument to amity between the two nations commissioned by railroad executive Sam Hill in 1921.

The arch stands precisely on the border, at the center of an international park: Citizens of either nation can pass without passport or visa into the other nation’s territory, provided they don’t stray beyond a dedicated area.

The U.S. side of the arch bears the inscription “Children of a common mother,” and the Canadian side reads “Brethren dwelling together in unity.” An iron gate stands open on either side, and an inscription above reads “May these gates never be closed.”