Pack
River length
Round
1
Score
0
Best
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Photograph of Kızılırmak River

Kızılırmak River

Turkey

1,355

kilometres

The wide Madeira River under a cloudy sky, forest on both banks

Madeira River

Bolivia and Brazil

?

more, or less?

© Wilson Dias/ABr · CC BY 3.0 br

River length

Two of 124 — one shows its kilometres, the other hides it. Say whether the hidden one is more or less and keep going. A tie counts as correct; one wrong answer ends the run, including a near miss within 10%.

A river is the one landmark nobody sees whole. A mountain can be taken in from a distance and a city from a hill, but a river is only ever met at one point on its way somewhere else: a bridge, an embankment, a stretch of towpath. How long it is has to be taken on trust, and what people trust instead is how important it seems — how many capitals sit on it, how often it turns up in history, whether a border follows it.

That is a fine way to rank rivers by fame and a poor way to rank them by length. The Thames runs through more of English history than any other river and is shorter than the Severn. The Jordan is 252 kilometres long. The Rubicon, whose crossing started a civil war, is 35.

Why the intuition fails

Fame gathers where people do, and people gather on the lower reaches of rivers, where the land is flat, the water is navigable and the sea is close. The rivers of Europe's great cities are short by world standards because Europe is small and has coasts on three sides; nothing in it has room to run far. The Rhine, the busiest waterway in Europe, is under a third the length of the Lena.

The Lena is the better lesson. Siberia has several of the longest rivers on Earth, and few people live along most of their length. Their names mean little outside Russia, because what makes a river famous is what happens on its banks, and for thousands of kilometres at a time nothing much does.

Naming makes it worse. Which of two rivers keeps its name after they meet was decided by whoever settled there first, not by which was longer. The Irtysh is a tributary of the Ob and runs some six hundred kilometres further than it. The Missouri, which joins the Mississippi above St. Louis, is within a few dozen kilometres of it on the record, and measured from the Missouri's source the combined river is one of the longest in the world.

What the data is and what it is not

The list leans towards rivers written about in many languages, and that means Europe, and Russia in particular. Fifteen of the rivers here flow through Russia and nowhere else. Germany is well represented by rivers most British players could not place. Britain, by the same measure, has two: the Severn and the Thames.

Every length is in kilometres, and every river in the list states it in kilometres, so no figure had to be converted. The thing that nearly went wrong was the definition of a river. At a slightly lower bar the same query returns a lake in Japan and a desert valley in Jordan, both of which Wikidata classes somewhere in the family tree of rivers, and both of which would have been dealt as a card with a length.

Questions

What does length mean here?
The length Wikidata records for the river, in kilometres, from its source to its mouth. Both ends are choices. A river rarely has one obvious source, and where a river becomes an estuary or a delta is a matter of definition, so two careful surveys of the same river can differ by hundreds of kilometres. The figure here is the one on the record, not a ruling on which survey was right.
Why is my river missing?
The likeliest reason is that it has fewer than 70 pages across Wikimedia’s projects, which is the bar for recognisable. At the September 2026 retrieval the Trent, the Clyde and the Shannon all fell short of it. After that: its record gives more than one length with nothing to say which is meant, as the Murray’s and the St. Lawrence’s do.
How accurate are the lengths?
Less accurate than they look. A river’s length depends on the scale of the map it is measured on, because a finer map follows more of every bend, and no two sources measure at the same scale. Some records give a length to the ten metres, most to the kilometre, and many are round hundreds. Treat any two rivers within a few per cent of each other as a coin toss that the record has settled.
Why does a card show a region instead of countries?
Where a river crosses more than three countries, the card names the region instead, because a list of nine countries does not fit under a name and would not help anyone guess. Otherwise it names the countries in the order the river flows through them. The line is written by hand: the record lists every country in a river’s basin, in no order, including some it never enters.
Does the pack change?
Rarely. A river’s recorded length changes when someone remeasures it or settles on a different source, and either is a correction rather than a drift, so the pack is marked evergreen rather than given a refresh timer. A regeneration re-runs the same query and rewrites only what changed.
Can I play it without JavaScript?
You can read all of it and see the opening pair, because the page is built as HTML before anything runs. Guessing needs JavaScript, since there is no server to send a guess to.

Where the figures come from

  • Wikidata, under CC0 1.0. Retrieved 2026-09-22.

    Rivers with at least 70 Wikimedia sitelinks, so every item is recognisable on sight (brief §15). Lengths are taken from the best-ranked statement and only where it is stated in kilometres. A river whose best-ranked statements still give more than one length — usually the river alone beside the river with its longest headwater — is left out rather than given a number we would have to choose. The countries beneath each name are written by hand, in the order the river flows.

Data updated 22 September 2026. a river's stated length changes when someone remeasures it or moves its source, and either is a correction rather than drift. The selection barely ages: a river's sitelinks grow slowly.

Image credits