BBC News

WEST BANK

Israel says the West Bank barrier is essential to protect itself from attack but to the Palestinians, it is an "apartheid wall".

NORTHERN IRELAND

Designed as a temporary measure to keep fighting Protestant and Catholic communities apart, many "peace walls" are stills standing.

SAUDI ARABIA

The most powerful economy in the Gulf is building one of the longest, most high-tech security fences in the world, at a cost of $300m.

CEUTA AND MELILLA

Residents of Spain's north African enclaves live behind towering fences, designed to keep out would-be illegal migrants trying to reach Europe.

CYPRUS

Built after the 1974 war, the no-man's land between Greek and Turkish Cypriots on the island remains under UN control.

PAKISTAN-IRAN

Baluchistani communities are divided by Iran's barrier on its border with Pakistan, intended to keep out smugglers and migrants.

RIO DE JANEIRO

Brazil says the walls are to protect the forest from growing shanty towns, but critics say they are an attempt to hem in the city's poor.

US-MEXICO

The US spends millions of dollars on a vast fence and surveillance operation along its southern border to try to keep illegal migrants out.

INDIA-PAKISTAN

The mined and heavily guarded border between India and Pakistan is one of the most volatile frontier regions on the planet.

KOREAN BORDER

The heavily guarded "De-militarized Zone" (DMZ) between North and South Korea remains a symbol of Cold War on the peninsula.

WESTERN SAHARA

Morocco's wall of sand in the Sahara desert is an attempt to keep out the Sahrwari people, who also claim the territory as their own.

BOTSWANA-ZIMBABWE

Botswana's hopes the extensive fence will protect its valuable livestock from disease, but Zimbabwe says its real purpose is to keep people out.