Interesting borders

An enclave is a country or territory entirely surrounded by another. Examples of enclave countries are San Marino (surrounded by Italy) and Lesotho (surrounded by South Africa).

An exclave is a part of a country or territory which is not contiguous with the rest of its land area, but on the same land mass. Some examples are Alaska of the United States, and Kaliningrad Oblast of Russia.

A tripoint is the conjunction of three countries or territories. These are fairly common; quadripoints (conjunctions of four countries or territories) or higher-level conjunctions are rather unusual, and mostly appear in a colonial context, in which borders have been defined by straight lines between coordinates, rather than natural features. There are a couple of near-quadripoints, at which four countries or territories are within a short distance.

Up a lazy river: there's just something about river border posts. A good example is the Mekong river ferry between Vietnam and Phnom Penh in Cambodia, where the boat draws in to the mudbanks and you skitter on planks up to the border station. Picture palm trees, louche officialdom, and a ceiling fan turning lazily.

Traffic switch, when a drive-on-the-right country meets a drive-on-the left – somewhere between them is a mixture of dodgems and wacky races. Examples are Thailand with Laos, Cambodia and Myanmar, Pakistan with China, Iran and Afghanistan, and mainland China with Hong Kong and Macau. Regimental histories gloss over this point, but one of the dangers of the Khyber Pass was the Torkham traffic switch on the Pakistan-Afghanistan border.

Except enclaves and exclaves there are many border anomalies to be found. Also, structures build at or by the border may have their oddities. Sometimes these are the results of border having changed.

Rail lines and roads that serve one country may pass through a neighbour. Examples include Berlin's U-Bahn during the Cold War (when the city was split by the Iron Curtain), the Trans-Siberian Railway passing through Kazakhstan (which was part of the empire when the railway was built) and the Saatse Boot, an Estonian road also partly getting on the wrong side of a new border.

In some cases, the only practical route into a settlement may pass through another country. This is often caused by a border river changing its course, leaving some territory on the wrong side of it. Sometimes, building a road to a remote settlement may not be feasible. A border "conveniently" placed along a river or a certain latitude may totally ignore local specifics, such as cutting off a peninsula, or cutting through the land of local communities. On the Finnish-Swedish border in the Torne Valley, most every village has one part on each side of the border river.

Sometimes, infrastructure is deliberately build at the border, to serve both sides. This is the case for some airstrips, which use border crossing facilities on a nearby road, novelty golf courses – which may straddle time zones too, and use differences in booze policy to their advantage – and some "friendship" constructs, such as the Québec-Vermont library or, less friendly, the Joint Security Area of the Koreas.

Infrastructure may also have been built on the wrong side of a border, perhaps before the border was surveyed. The Russian Empire probably didn't much care about the border through the Märket islet when they built a lighthouse there, causing quite some headache for a 1980s border survey.

Here are some borders that have been especially agreeable to cross in the early 21st century:

• 🌍 Baarle (Belgium and the Netherlands). The Belgian border takes some strange twists and turns, and at Baarle it excels: it's as if a map of the Belgian section of town was etched on glass then dropped. There are shards of Belgium within the Netherlands, and vice versa, sometimes within the same building. Cobbles mark the border and the main issue for visitors is different pub rules: police on each side have little else to do but usher transgressors back across the cobbles to where their behaviour is legal. 
• 🌍 Vatican City. The Vatican has just a low chain fence dividing St Peter's Square from the City of Rome in Italy, easily stepped over. (The other entrances, e.g. to the Vatican Museum, aren't so distinctive.) Street drinking offences aren't a factor unless you've got in with an unusually bibulous set of Cardinals. But contemplate the long centuries in which the Papacy was a temporal power, with similar sanctuary lines drawn across many Italian city-states. 
• 🌍 Nicosia (Greek and Turkish sectors of Cyprus). The Ledra Street pedestrian crossing is within a bazaar. You might even struggle to locate it among the cafes and piles of cheap jeans, until you realise that the fellow getting in your face isn't offering "free coffee and halva, please step in no obligation to buy, but really does need to see your passport. The vehicle crossing is more convenient for the must-see museum but is more like a parking lot entrance, just a metal bar across a potholed lane. 
• 🌍 Panmunjeom (South Korea and North Korea). The site where the 1953 armistice was signed is now a visitor attraction with three conference rooms straddling the border. It can be visited from either side provided you join a guided tour, and you can briefly cross over to the other Korea within the confines of one of the conference rooms. However, the exit to the other side will be guarded by soldiers, and you will not be able to proceed any further. 
• 🌍 Canusa Street (Stanstead in Quebec, Canada and Beebe Plain in Vermont, United States of America). Crossing the street will result in your ending up in a different country. However, this is no longer allowed since 9/11, and you now have to report to border control at the western end of the street if you want to cross it. The Haskell Free Library and Opera House straddles the border, and you can freely hop across the border while inside the building. Although the entrance is on the American side, visitors from the Canadian side may cross the border to immediately enter the building without passing through border control as long as they follow a specific path. (updated Dec 2023)
• 🌍 Chung Ying Street, literally "Sino-British Street" (Runs along the border between Sha Tau Kok in Hong Kong and the district of Shatoujiao in Shenzhen, mainland China). One side of the street is in Hong Kong (that used to be British), and the other in mainland China. As the Hong Kong side is within the Frontier Closed Area, only Sha Tau Kok residents are permitted to visit from the Hong Kong side. All Chinese citizens may visit from the mainland Chinese side provided they obtain a permit in advance, but this permit is not available to foreigners. 
• 🌍 Saatse Boot (The road between Värska and Ulitina). A legacy of the time when both were part of the Soviet Union, both ends of the road are in Estonia, but a small segment of it passes through Russia. No Russian visa is required to drive or cycle on this road, though you are required to drive or cycle continuously and may not stop or walk while inside Russia, and you may also not leave the road to travel to the rest of Russia. 
• 🌍 Madha. An exclave of Oman surrounded entirely by the United Arab Emirates, which in turn surrounds the enclave of Nahwa which belongs to the UAE. 
• 🌍 Keinovuopio. The northernmost permanently inhabited places in Sweden, Keinovuopio and Kummavuopio, have no road from the rest of the country, just a pedestrian suspension bridge over the border river from Finland (where a highway passes by). No official border crossing here, but who cares? 
• 🌍 Wagah-Attari (The main crossing between India and Pakistan). Only open until sunset, when there's an elaborate military closing ceremony. Tattoo? – it's almost camp. Join the onlookers in the bleachers if you can. 
• 🌍 South Pole. While Antarctica is terra nullius not belonging to any country, several countries have made claims on the continent between specified longitudes. As these claims meet at the South Pole, it is a rare case of seven territories meeting at one point. 
• 🌍 Four Corners (United States). The quadripoint for the states of Arizona, Colorado, New Mexico, and Utah. 
• 🌍 Four Corners (Canada). A quadripoint between the provinces of Saskatchewan and Manitoba, and the territories of Northwest Territories and Nunavut, achieving its status in 1999 as Nunavut was founded. 
• 🌍 Kazungula. A near-quadripoint where Zambia has a few hundred metres of Botswana in the river Zambezi, separating Namibia from Zimbabwe. 
• 🌍 Three Country Cairn (Treriksröset, Treriksrøysa, Kolmen valtakunnan rajapyykki) (near Kilpisjärvi). The tripoint between Sweden, Finland and Norway is the world's northernmost, and also Sweden's northernmost point. It can be reached by hiking from the nearest villages or from the ferry quay. 
• 🌍 Märket lighthouse. A skerry in the Åland archipelago, shared between Sweden and Finland. A lighthouse was built in 1885, as the island was the westernmost point of the Russian Empire; however on the Swedish part of the island. In 1985, the border was adjusted so the lighthouse stands on Finnish soil. 
• 🌍 Penon de Velez de la Gomera (Spanish North Africa and Morocco). An isthmus of 85 metres, said to be the world's shortest national border. 
• 🌍 Bir Tawil (North Africa). Terra nullius on the border of Egypt and Sudan, part of a larger border dispute where each country had to choose between claiming this tiny landlocked parcel or claiming a better piece of land elsewhere on the same border. 

These we have lost: the DDR – West Berlin border so long as you had a western passport and money in your pocket. Checkpoint Charlie is the best known but even more curious was Checkpoint Friedrichstrasse, with metro platforms and trains for both east and west city networks separated by five lethal metres of track.

• Fortifications
• Police and military ceremonies