The US-Mexico border is known for two things - violence and smuggling. Americans talk about the border that protects them from crime, drugs, and other bad things they see as Mexican problems.
Today the UK-Ireland border is peaceful and open. But the conflict, rooted in the centuries long legacy of British colonialism, is hardly resolved. It lies just below the surface of daily life.
For the last 22 years, Northern Ireland's fragile peace has been based on the fact that the Irish border is essentially open. Brexit has thrown that arrangement into total uncertainty.
The Kenya-Tanzania border straddles some of the world's best known nature reserves and safari destinations. There, environmental and commercial concerns come together.
The land border between Kenya and Tanzania, combined with the Swahili Coast and its sea border on the Indian Ocean, is a crucial node in multiple international smuggling networks.
The long and grinding collapse of Venezuela's economy has pushed more than five million Venezuelans to leave the country in search of work, medical care, and other basic necessities.