Historic sites — how this layer is made

What you are looking at

Each dot is a historic site. There are more than one million worldwide. Colour represents what kind of thing it is, and the size of a dot represents the footprint of the site. Click on any of them to see what OpenStreetMap records, such as when it was built, which civilisation it belongs to and whether it is protected. If there's a Wikipedia article, we show a short summary and a link to the full article, in your own language where possible.

Where the data comes from

Every site here is something a mapper added at the OpenStreetMap website, from a survey, from aerial imagery or from a local heritage register. We don't model or estimate anything ourselves.

What we include

Every value of the `historic` key except a few. We start from all of them and leave a kind out only for a reason, because a list of the obvious kinds would quietly drop whatever nobody thought of. We leave out four:

Memorials, wayside crosses and wayside shrines, which together are more objects than everything else in the key combined. A roadside cross is a marker rather than a site you visit, and crosses and shrines are near-universal in alpine Europe and near-absent elsewhere.
Charcoal piles, a soil trace of historic burning, which is invisible on the ground and mapped almost only in a few German forests.
`historic=yes` and `historic=no`, which say "historic, unspecified" and "not historic at all".
Former administrative areas, islands, waters and boundaries. About twenty exist, each drawn at national scale, and sized by area they would have been the largest marks on the map.

We also leave out anything mapped as a line, so most Roman roads, hollow ways, city walls and historic railways are absent.

Colour

Colour represents the kind of site, grouped from OpenStreetMap's own values into ten classes. We group values only where they are the same kind of thing at a different level of detail, such as a castle wall with a castle. The ten classes cover nearly all of the map, and a long tail of rare kinds is drawn in grey. Shielings, the ruined summer huts of Scotland and Norway, count as archaeological sites, because a class of their own would paint the Highlands one colour for a tag used almost nowhere else. Churches and monasteries count as buildings, because a historic church is normally tagged as a place of worship instead.

Sites with no name

Fewer than half of these sites record a name, and we show the unnamed ones just the same. A site with no name is one nobody has published a name for rather than one that isn't there. Showing only the named sites would mislead you badly, because naming is much thinner for sites recorded from survey, and thinner for war graves and mine workings than for castles.

Size

The size of a dot represents the footprint of the site in square metres, which is physical extent rather than importance. A large archaeological landscape covers more ground than a castle keep, and the map says nothing about which matters more. Sites mapped as a single point are drawn at one nominal size.

Where the map is empty

An absent site means nobody has mapped it yet, not that nothing stands there. Coverage is strongest across western and central Europe. What counts as historic also depends on what a local mapping community treats as heritage, and boundary stones and milestones, which we keep, are mapped densely across parts of Europe and hardly at all elsewhere. Read a dense patch as a well mapped place first and a historically rich one second.

Up to date, mostly

OpenStreetMap is edited continuously, and we take a new copy once every one to three months. OpenStreetMap's edit history records when a feature was mapped rather than when it was built or lost, so there is no year control here.

Source and licence

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