China's military spending was $215.7bn in 2016. Given that it shares a border with more territories than any other country, perhaps that should not come as a surprise.

The most populous nation on the planet has 16 unique land neighbours, with 22,147km of land borders (also a record).

They are: Afghanistan (76km), Bhutan (470km), Hong Kong (30km), India (3 borders totalling 3,380km), Kazakhstan (1,533km), North Korea (1,416km), Kyrgyzstan (858km), Laos (423km), Macau (0.34km), Mongolia (4,677km), Myanmar (2,185km), Nepal (1,236km), Pakistan (523km), Russia (2 borders totalling 3,645km), Tajikistan (414km) and Vietnam (1,281km). That's a lot of armed guards and passport control stations.

A couple of its borders are particularly interesting. Trains crossing between Mongolia and China need to have their wheels changed at the town of Erlian. That's because railway tracks in China are narrower than in Mongolia. It takes several hours to perform this monumental operation and passengers must remain on board throughout.

Those who scale Everest can not only brag of climbing the world’s highest peak, but can also claim to straddle the world’s highest border: this icy peak is a natural frontier between Nepal and China.

The border between China and North Korea, meanwhile, is one of the world's most heavily guarded, what with territorial disputes, escape attempts from Kim Jong-un's regime, and fears over Pyongyang's nuclear ambitions. There have even been reports of North Korean soldiers darting over to China to steal food and money.

Which other countries have a surfeit of neighbours?

Russia

Number of unique land neighbours: 14

Total length of borders: 20,017km

Neighbours: Azerbaijan, Belarus, China, Estonia, Finland, Georgia, Kazakhstan, North Korea, Latvia, Lithuania, Mongolia, Norway, Poland, Ukraine.

Given that it's the world's largest nation by area, it will not be a shock to learn that Russia has 14 land neighbours. It also shares a quirky maritime border with the United States. Separated by the Bering Strait, which forms a natural border between Russia and the US, the Diomede Islands are comprised of Big Diomede and Little Diomede.

Russia owns the former and America owns the latter. As you can imagine, the frontier is frosty in more ways than one (it’s actually illegal to cross the strait). More interesting, though, is the fact that Little Diomede is almost a day behind its bigger sibling, meaning islanders can look across the water and see the future.

Brazil

Number of unique land neighbours: 10

Total length of borders: 14,691km

Neighbours: Argentina, Bolivia, Colombia, French Guiana, Guyana, Paraguay, Peru, Suriname, Uruguay, Venezuela.

Nearly every other South American nation shares a border with Brazil, with the only exceptions being Chile and Ecuador.

Brazil is linked by land to nearly every country in South America Credit: f11photo - Fotolia

Democratic Republic of the Congo

Number of unique land neighbours: 9

Total length of borders: 10,730km

Neighbours: Angola, Burundi, Central African Republic, Republic of the Congo, Rwanda, South Sudan, Tanzania, Uganda, Zambia

Its vast size and location at the very centre of Africa, the continent with more countries than any other, means the Democratic Republic of the Congo has nine land neighbours. It is nearly landlocked, retaining just a 37 kilometre strip of Atlantic coastline. Only five countries possess a smaller coastline, including Jordan (26km), Nauru (30km), Tuvalu (24km), Monaco (4.1km) and Bosnia and Herzegovina (20km). There are 45 landlocked nations.

Germany

Number of unique land neighbours: 9

Total length of borders: 3,621km

Neighbours: Austria, Belgium, Czech Republic, Denmark, France, Luxembourg, Netherlands, Poland, Switzerland.

Germany's most famous border was torn down in 1989, but it still has plenty of them. While Africa has more countries than any other, Europe's smaller size (not to the mention its Schengen Agreement) makes it perfect for travellers hoping to tick off lots of countries in the shortest possible time. In 2016, ahead of the Brexit referendum, Jonathan Thompson managed to visit every country in the EU (30 countries in total) in just over a month.

France

Number of unique land neighbours: 8

Total length of borders: 2,889km

Neighbours: Andorra, Belgium, Germany, Italy, Luxembourg, Monaco, Spain, Switzerland

Eight countries border mainland France, but if one factors in its overseas territories and departments, such as French Guiana, its number of land borders jumps to 11.

Austria

Number of unique land neighbours: 8

Total length of borders: 2,562km

Neighbours: Czech Republic, Germany, Hungary, Italy, Liechtenstein, Slovakia, Slovenia, Switzerland

Austria is equally endowed with land neighbours. Its shortest border is a 35km strip that links it with Liechtenstein; its largest the 784km border it shares with Germany.

Zambia

Number of unique land neighbours: 8

Total length of borders: 5,667km

Neighbours: Angola, Botswana, Democratic Republic of the Congo, Malawi, Mozambique, Namibia, Tanzania, Zimbabwe.

Zambia's shortest border is the 150-metre strip of land that touches Botswana near Kazungula. Only one border on Earth is less significant, the 85 metres that divides Morocco from the Spanish exclave of Peñón de Vélez de la Gomera.

Turkey

Number of unique land neighbours: 8

Total length of borders: 2,648km

Neighbours: Armenia, Azerbaijan, Bulgaria, Georgia, Greece, Iran, Iraq, Syria.

No border causes more headaches than the 822km that Turkey shares with Syria. The area surrounding it is off-limits to British travellers, according to the Foreign Office.

Turkey shares a border with eight other states Credit: muratart - Fotolia

Tanzania

Number of unique land neighbours: 8

Total length of borders: 3,861km

Neighbours: Burundi, Democratic Republic of the Congo, Kenya, Malawi, Mozambique, Rwanda, Uganda, Zambia

Serbia

Number of unique land neighbours: 8

Total length of borders: 2,027km

Neighbours: Bosnia and Herzegovina, Bulgaria, Croatia, Hungary, Kosovo, Macedonia, Montenegro, Romania

The last of six countries with eight land neighbours is Serbia. While Serbia and Kosovo share a border, Serbia does not recognise the republic as a sovereign state. Travellers attempting to enter Serbia with Kosovo stamps in their passport have even been turned away.