As Donald Trump jumpstarts his election manifesto pledge to build a 'big, beautiful wall' along America's border with Mexico by signing two executive orders, many countries around the world rely on nature or ingenuity for their borders.
Borders between countries can be separated by lakes, gorges on a river, crossings on a mountain - and even a lick of paint, as is the case in the village of of Baarle-Hertog between Belgium and the Netherlands.
Some borders are spectacular - such as the awe-inspiring Iguazu Falls - that separates the Brazilian state of Paraná and the Argentine province of Misiones.
Borders between countries can be separated by lakes, gorges on a river, crossings on a mountain - and even a lick of paint, as is the case in the village of of Baarle-Hertog between Belgium and the Netherlands.
Some borders are spectacular - such as the awe-inspiring Iguazu Falls - that separates the Brazilian state of Paraná and the Argentine province of Misiones.