Eight Borders That Make No Sense, and the Reason Each One Exists

Borders look permanent because they are printed, and almost all of them are the frozen result of something temporary: a treaty, a war, a survey, a river, or an argument between two landowners several centuries ago.

Here are eight of the strangest, with the cause of each.

1. The enclaves inside enclaves

The border between India and Bangladesh included, until 2015, an extraordinarily complex arrangement of enclaves: pieces of one country entirely surrounded by the other, and in some cases pieces of one country inside an enclave of the other inside the first.

The usual explanation is that the pattern descends from arrangements between local rulers long predating either modern state, which were then inherited by successive administrations and never rationalised. Tens of thousands of people lived in territory they could not legally leave without crossing a border, with severe practical consequences for schooling, healthcare and policing.

The two countries resolved it in 2015 by a land boundary agreement that exchanged most of the enclaves and allowed residents to choose their citizenship.

2. The border through a building

Where an international boundary predates a building, the building sometimes gets built anyway.

There are documented cases of a border running through a library, a hotel and private houses, with lines marked on floors and, in at least one case, different national rules applying to different rooms. These are curiosities in practice because the countries involved cooperate, but the administrative arrangements behind them are genuinely intricate.

3. The line drawn with a ruler

A very large proportion of borders in Africa, the Middle East and the western United States are straight.

Straight borders indicate one thing: they were drawn by people who were not there, on a map, before the territory was surveyed in detail. In the colonial partitions of the nineteenth century this was explicit policy, and the consequences — borders that cut across linguistic, ethnic and trading geographies — are still being worked through.

4. The river that moved

Rivers make convenient borders and terrible ones.

Where a boundary follows a watercourse, the law generally distinguishes between gradual change, where the border moves with the river, and sudden change, where the border stays where the river used to be. The result over a century is a boundary that no longer follows the water at all, leaving parcels of one country on the wrong bank.

Several long-running international disputes come down to exactly this distinction.

5. The country you can only reach through another

Some territories are practically inaccessible from their own country without crossing someone else’s.

This arises when a border follows a watershed or a straight line that ignores the actual terrain, leaving a valley whose only road runs the other way. Local arrangements — transit agreements, shared roads, special crossing rules — usually develop to make daily life workable.

6. The border that was never agreed

A number of international boundaries are marked on maps with dashed lines because the two parties do not agree where they are.

Map publishers deal with this in different ways depending on where they are publishing, which is why the same map of the same region can look materially different in two countries.

7. The disappearing border

Within a customs or travel union, a border can become invisible in practice while remaining fully legal.

That produces an odd situation where the line still matters enormously — for tax, for law, for citizenship — while having no physical presence at all, and it can reappear very quickly if the political arrangement changes.

8. The border that exists because of a misdrawn survey

Several boundaries are not where the treaty says they should be, because the original survey contained an error that was subsequently built on.

The general principle in most such cases has been that a marked and long-accepted boundary takes precedence over the text that produced it. In other words, once everyone has lived with the mistake for long enough, the mistake becomes the border.

The pattern

Almost every strange border comes from one of four things: an inherited arrangement nobody rationalised, a feature that moved, a line drawn remotely, or an error that was accepted.

None of them is random, and that is the useful point. A border that looks absurd is almost always a fossil of a decision that made sense to somebody at the time.