GRID · MAJOR DAMS
The Great Walls of Water
A dam is among the largest things humans build: a wall thrown across a river to hold back a lake, for hydropower, flood control, irrigation or water supply. This layer maps the world’s major dams as 4,256 dam-wall marks — the structure itself, the civil-engineering twin of the hydroelectric stations bolted onto many of them. There is a catch in the data: both OpenStreetMap and Wikidata catalogue some 80,000 dams (mostly tiny weirs), and the recorded height is sparse andriddled with unit errors — feet logged as metres, producing “dams” taller than any that exist. So ranking by height would be a fiction. Instead the set is ranked by notability— how many Wikipedia language editions cover each dam — and cut at three or more. That surfaces the genuine global roll-call (Three Gorges, Aswan, Hoover, Itaipu, the Grand Ethiopian Renaissance Dam, Nurek, Kariba), and because renown isn’t skewed by mapping completeness, it makes this the most globally-balanced layer on the canvas. Tap a mark for its name, height, country and year.
Ranked by how widely the world knows them
With height unusable as a ranking, the map leans on a signal that isclean: how many Wikipedia language editions write about a dam. A structure covered in dozens of languages — Three Gorges sits in over a hundred — is genuinely world-famous; one in three or four is a notable regional landmark. The world-iconic dams anchor the globe at world view and the rest reveal as you zoom. Here is how the set divides:
The world’s most renowned dams
Sorted by the same notability signal, the top of the list reads like a roll-call of the planet’s great water works — and it spans every continent, not just the rich and well-mapped ones. The bar shows relative renown (Wikipedia language coverage); the figure on the right is the dam’s height where a physically plausible one is recorded (anything implausibly tall is dropped as a unit error rather than shown):
A genuinely global map
This is where ranking by renown pays off. The other OpenStreetMap point layers on this canvas lean heavily European because that is where mapping is most complete — but notability doesn’t care how well a country is mapped, so this set follows the realdistribution of the world’s great dams. East Asia leads, on the back of China’svast dam-building boom; North America’s historic giants and the major projects of the Middle East, Africa and South Asia all show in proportion; Europe is just 11%— the opposite of the layers around it.
About this data
Every dam comes from Wikidata (instances and subclasses of dam with coordinates, CC0). Of the ~80,000 catalogued, this layer keeps the 4,256 covered by three or more Wikipedia language editions, a notability cut chosen becausethe obvious alternative — height — is recorded on only a fraction and is badly unit-contaminated (feet stored as metres). Height is therefore never used to size or rank; it is shown in the tap on the 38% (1,624) of dams that carry a physically plausiblevalue (0–305 m, the real world record), and dropped where it isn’t. Every dam is a single mark — colour, not size, because there is no honest size axis — with the iconic drawn first and the rest revealing on zoom. Bridges and causeways that Wikidata files under the dam tree (the King Fahd Causeway and the like) are filtered out; a few famous sea-dams and dike systems (Afsluitdijk, Kinderdijk) are kept, as they genuinely hold back water. Operators are never shown (the no-recon rule). Coordinates come straight from Wikidata, not hand-placed. Snapshot taken 2026-06-27.