Museums — how this layer is made

What you are looking at

Each point is a museum — a feature tagged `tourism=museum` in OpenStreetMap. 108,292 of them worldwide, drawn as a coloured dot sized by footprint area and coloured by subject, where a subject has been recorded. At the closest zooms the dot is joined by the building's mapped outline, where one has been drawn.

Click any museum to see what OpenStreetMap records about it — its subject, whether it charges for entry, who runs it, and the year it opened. Where the museum has a Wikipedia article, a short summary is fetched live and shown in your own language; and every museum links to the OpenStreetMap object it came from.

Mapped, not modelled

Each museum is an object a mapper drew, from survey, local knowledge or aerial imagery; nothing here is modelled or estimated. The limitation is therefore completeness, not resolution: an unmapped museum is absent, and on this map absence looks identical to empty ground.

Colour, and how much of it there is

Colour shows the subject — and about four museums in five do not say what theirs is. They are drawn in grey.

The subject tag is on 21.8% of museums. Grey is therefore a real, named category here: it says nobody recorded the subject, not that the museum has an unusual one. Nothing else on these features says more — who runs a museum and whether it charges are useful facts, but neither tells you what it is about.

Ten subjects have their own colour, and they are the ten commonest. In size order: history (9.0% of all museums), local history (3.1%), art (2.6%), transport (1.4%), science and technology (1.1%), natural history (1.0%), a single person (0.8%), archaeology (0.7%), military history (0.6%), and open-air or living-history museums (0.5%). Everything else — children's museums, agriculture, ethnography and a long tail of one-off subjects — shares a single "other" colour. That is a limit of what a legend can carry legibly, not a judgement about which museums matter.

Several near-synonyms are folded together before the map is drawn, so the classes are not exactly OpenStreetMap's raw values: a gallery is filed under art; natural history, geology and palaeontology under natural history; railways, ships, aircraft and cars under transport. Click a museum and you see the value OpenStreetMap actually holds.

Size

Each symbol is sized by footprint area — the ground the mapped outline covers, in square metres measured on the globe. Symbol area is proportional to footprint (radius to its square root), so a museum four times the area draws twice as wide.

Size is building size, and on this layer that is a weak guide to anything else: the selection runs from a national institution to a one-room local collection in a converted cottage, and an open-air museum covering a hillside outsizes any of them. Many museums are mapped as a single point with no outline at all; rather than draw them all at the smallest size, they are given a nominal, typical size.

Charges and opening

Whether a museum charges for entry is shown where OpenStreetMap records it — on about a fifth of them. It is what the tag said when this copy of the map was taken, and prices and policies change; treat it as a hint rather than a promise, and check with the museum.

Opening hours are not shown, although OpenStreetMap holds them for more than a quarter of these museums. They are recorded in a compact machine syntax that has to be interpreted and rewritten for each language to make sense to a reader, and showing the raw string would be worse than showing nothing. It is on the list.

Completeness

OpenStreetMap is not equally complete everywhere. Coverage is strongest in Western and Central Europe and other well-mapped regions, and thinner in low- and middle-income countries. An absent museum means "not yet mapped", not "does not exist". A dense patch here is a well-mapped place first, and a museum-rich one only second.

A picture of the present

Today's map, not a history. OpenStreetMap is edited continuously; this copy is refreshed periodically. There is no year control, and a museum that closed some time ago may still be mapped until a mapper updates it.