A triple border point, or tripoint, is a spot where the borders of three countries meet. As of 2020 the world had 181 international tripoints. Nearly half are in rivers, lakes or seas, and the rest are marked on land by anything from a numbered pillar to a concrete cone standing in a lake. China has the most, with 16. Most tripoints draw little attention, but a few matter a great deal. Where a treaty is vague, three governments can each place the point somewhere different, and in 2017 exactly that sort of disagreement brought Chinese and Indian troops face to face on a Himalayan plateau.
Doklam, 2017: Two Armies and a Disputed Point
On 16 June 2017, Chinese troops with construction vehicles began extending a road south across the Doklam plateau, a high pasture where China, Bhutan and the Indian state of Sikkim come together. Both China and Bhutan claim Doklam. India makes no claim to it but backs Bhutan's position. Two days later, about 270 armed Indian soldiers with two bulldozers crossed from Sikkim to stop the work, in what India called Operation Juniper. On 29 June Bhutan formally protested, saying the road was being pushed toward its army camp at Zompelri near the Jampheri ridge, about 2 km to the south.
The standoff lasted until 28 August, when both India and China announced that they had pulled their troops back from the site. Its core was a question about geography: where exactly do the borders of China, Bhutan and India meet? China's foreign ministry argued that a tri-junction "is a point", not an area, and said Indian troops had crossed the Sikkim–China border about 2,000 metres from where China places it. India's foreign ministry pointed to a 2012 understanding between the two governments that the tri-junction points would be settled together with the third country involved, and said China's road building had changed the status quo.
The ridge matters for military reasons. Indian security analysts argue that holding the plateau would give China a view down the Chumbi Valley, would outflank India's defences in Sikkim, and would overlook the Siliguri Corridor, the narrow strip of Indian land that links the country's northeast to the rest of India. Chinese officials describe Doklam as traditional pasture for herders from Yadong County in Tibet. They say that before the 1960s Bhutanese herders needed Chinese consent to graze there and paid a grass tax to China, and that Tibetan archives still hold receipts for it.
Mount Gipmochi or Batang La: Reading the 1890 Convention of Calcutta
The dispute goes back to a treaty that Bhutan did not sign. In the 1890 Convention of Calcutta, Britain and Qing China defined the boundary between Sikkim and Tibet as the crest of the mountains dividing the waters of the Teesta, which flows into Sikkim, from the waters of Tibet. Article I says the line "commences at Mount Gipmochi on the Bhutan frontier". China reads that phrase as fixing the tripoint at Gipmochi.
There are two problems with that reading. First, nobody had surveyed the area when the convention was signed, and the sketch maps of the time put Gipmochi directly on the main Dongkya range, with no plateau shown south of it. Second, Bhutan was not a party to the agreement, and there is no record that it was consulted. Unofficial maps later put the tripoint at Batang La, a peak on the northern ridge of the plateau. The historian Srinath Raghavan has argued that the watershed rule in the treaty's first sentence points to the Batang La–Merug La–Sinchela ridge as the China–Bhutan line, because Merug La (4,653 m) and Sinchela (4,429 m) are both higher than Gipmochi (4,427 m).
Bhutan and China have held 24 rounds of boundary talks since 1984, and they reached agreements in 1988 and 1998, the second of which rules out the use of force. Neither agreement settled where the tripoint lies, so the plateau remains a flashpoint. It is also only one section of the long Himalayan frontier discussed in our guide to the China–India Line of Actual Control.
Ulaanbaatar, 1994: How Three Governments Fix a Tripoint
Doklam shows why a tripoint can't be settled by two countries alone. A normal border treaty is bilateral, between two states, but the point where three borders meet involves all three, so its exact position often needs a trilateral agreement. The clearest example comes from Central Asia. On 27 January 1994 China, Russia and Mongolia signed a trilateral agreement in Ulaanbaatar that fixed both of the points where their three borders meet. At the eastern tripoint, Tarvagan Dakh, the treaty called for a marker. At the western one, the summit of Tavan Bogd in the Altai mountains, it said no marker would be built, and the mountain itself serves as the reference.
The number of tripoints a country has usually depends on how many neighbours it has. China has 16 international tripoints and Russia has between 11 and 14, depending on the source. Landlocked Austria has nine, two of them with Switzerland and Liechtenstein. Countries with only one land neighbour, such as Portugal and Lesotho, have none, and neither do the United States, Canada, Australia or Japan. The United States does have many state tripoints, plus one quadripoint, the Four Corners Monument.
Kazungula: The Quadripoint That Turned Out to Be Two Tripoints
Where the Chobe River joins the Zambezi, four countries come very close together: Namibia, Botswana, Zambia and Zimbabwe. Older sources described the spot as a quadripoint, a single point where all four meet. The borders here go back to the 1890 Heligoland–Zanzibar Treaty, which gave Germany the narrow Caprivi Strip so that its colony of South West Africa could reach the Zambezi. Whether Botswana and Zambia actually share a border became a live question in 1970. That year South Africa, which then occupied Namibia, told Botswana that the four borders met at one point and that the two countries therefore had no common frontier. On that basis it declared the Kazungula ferry between them illegal. Botswana rejected both claims. Shots were fired at the ferry, and some years later the Rhodesian army attacked and sank it. As late as 1979 the legal scholar Ian Brownlie wrote that a quadripoint could not be ruled out.
Between 2006 and 2010 all four states agreed that Botswana and Zambia share a boundary of roughly 150 metres across the river. That means two tripoints about 100 to 150 metres apart rather than one quadripoint. On that short frontage Zambia and Botswana built the 923-metre Kazungula Bridge, part of a US$259 million project that also built the border posts, opened to traffic on 10 May 2021 and replaced the ferry. The bridge is curved so that it stays clear of the Zimbabwean and Namibian borders on either side. Even so, it was reported in 2014 that Namibia had granted an easement for part of the crossing, since all three parties agreed that stretch lies in Namibian territory.
Lake Constance and Sia Kangri: Tripoints Nobody Has Pinned Down
Some tripoints are still undefined long after the countries around them stopped disputing anything else. Lake Constance lies where Germany, Switzerland and Austria meet, but apart from the shallow water under 25 metres deep near each shore, which belongs to the nearest country, there is no legally binding agreement on where the borders run. Switzerland holds that the border follows the middle of the lake. Austria considers the open water a condominium, shared by all three shore states. Germany's position is ambiguous. Shipping and fishing are governed by separate treaties.
In the Karakoram, the tripoint problem is different. About a kilometre southeast of the 7,422-metre summit of Sia Kangri, close to Indira Col at the head of the Siachen Glacier, is the point where the territories controlled by India, Pakistan and China meet. Because the land on every side is disputed, the point marks where the areas each country controls meet, not a boundary that all three governments accept.
Vaalserberg, Treriksröset and the Triple Frontier: Tripoints as Destinations
In Europe, where borders are open, tripoints have become places to visit. The Vaalserberg, a 322.4-metre hill outside Vaals, is where the Netherlands, Belgium and Germany meet. From 1830 to 1919 it was a quadripoint, because the tiny territory of Neutral Moresnet also touched the summit. Today a 50-metre tower on the Belgian side, opened in 1994, overlooks all three countries, and the Amstel Gold Race cycles past.
The Treriksröset, where Sweden, Norway and Finland meet, is the northernmost international tripoint in the world. The point itself is about 10 metres out in Lake Goldajärvi, 489 metres above sea level, and since 1926 it has been marked by a beige concrete cone on a pile of stones. Norway and Russia, which then ruled Finland, set the first stone there in 1897. Sweden did not add its stone until 1901. Hikers reach the cone on an 11-kilometre trail from Kilpisjärvi in Finland. From the Swedish side it takes a trek of at least 70 km each way.
The Triple Frontier, where the Iguazú River runs into the Paraná, is the most populated tripoint in the world, with about 950,000 people. Ciudad del Este in Paraguay had 299,255 residents in 2018, Foz do Iguaçu in Brazil about 258,000 in 2020, and Puerto Iguazú in Argentina 82,227. Each country has put up an obelisk in its own national colours on its riverbank, and from any one of them you can see the other two.
The Triple Frontier also shows that a tripoint can be a security concern. In 2002 the U.S. government said groups in the region were financing terrorist activity, and Paraguayan authorities alleged that Hezbollah and Hamas were operating there. No evidence for the claim was ever made public, and local politicians pointed out that no one there had ever been convicted of terrorism, and the three governments have coordinated border policing through a Tripartite Command based in Foz do Iguaçu since 1996.
Tripoints can also disappear when the countries around them do. From 1871 to 1918, the Three Emperors' Corner at the confluence of the Black and White Przemsza rivers near Mysłowice was where the German, Russian and Austro-Hungarian empires met. Before the First World War it drew between 3,000 and 8,000 visitors a week. After the First World War the Austrian and Russian sides passed to Poland in 1919 and the German side followed after the 1921 Upper Silesian plebiscite. The spot, now in an industrial area, has been marked by a memorial plaque since 2004. The Triple Frontier, by contrast, is busier than ever, a short drive from the falls described in our guide to Iguazú Falls.