What is it?

Pleiades+ is a toponym extension to Pleiades based on GeoNames that is a spinoff output of GAP. Pleiades provides URIs for ancient places, but (as yet) has only limited alternative toponyms. GeoNames is a much larger gazetteer of (mainly contemporary) locations, some with historic equivalents, and a much richer array of alternative toponyms. Pleiades+ attempts to match Pleiades and GeoNames identifiers together based on both location and toponym. When such matches are found, the additional toponyms from GeoNames are associated with the Pleiades URI.

Why is this useful?

We use this for geoparsing – identifying references to ancient places in texts. This is a two step process in which we must first tag possible references based on a string match with any entry in gazetteer. Secondly, where the same name may refer to multiple places we need to identify which is the correct one. This is partly done by taking into account places nearby so in both cases the more tags we have, the better our results. Increasing the number of toponyms increases the tagging rate which is good news for us. We also hope it will be useful for other people using digital identifiers for places in the ancient world.


In the interests of openness and collaboration we are making Pleiades+ freely available under a CC-zero license. This essentially means that you can do whatever you like with it but please take into account the HEALTH WARNING and remember that it’s always polite to give attribution, even when you don’t have to. It’s also good scholarly practice.


No list of alternative toponyms is, or ever could be, complete. Names simply don’t work that way. Pleiades+ is merely an attempt to add additional toponyms to Pleiades and makes no claims whatsoever about completeness. It provides about 50% more toponyms than the original Pleiades data, although the distribution tends to reflect many additional toponyms for relatively few sites, rather than many sites with one or two extra toponyms. Other things you should know are:

  • Currently it is only using data from a subset of GeoNames’ country datasets (see list below). As a result, it is not (yet) even a full ‘intersection’ of Pleaides and GeoNames.
  • Matching has been done automatically based on a) a toponymic match, and b) the point coordinates of GeoNames being within the grid_square of Pleiades/Barrington Atlas
  • The centroid coordinates, where present, relate to the Barrington Atlas grid square, not the place. We use these as a proxy for the location when geoparsing.

As time permits we will extend this page with a fuller set of instructions on how to regenerate Pleiades+ should you wish to. In the meantime, the original blog post lays out the fundamentals. Feel free to contact us for suggestions and code if necessary.

List of GeoNames countries and regions used (largely mediterranean, littoral): (AL) Albania, (BA) Bosnia, (CY) Cyprus, (DZ) Algeria, (EG) Egypt, (ES) Spain, (FR) France, (GR) Greece, (HR) Croatia, (IL) Israel, (IT) Italy,  (LB) Lebanon, (LY) Libya, (MA) Morocco, (MT) Malta, (PT) Portugal, (TN) Tunisia, (TR) Turkey


We are grateful to the folks at both Pleiades and GeoNames for making this work possible

Pleiades+ xlsx file (unfortunately WordPress won’t host zip or csv!)


To the extent possible under law,

Leif Isaksen

has waived all copyright and related or neighboring rights to
This work is published from:

United Kingdom.


5 Responses to Pleiades+

  1. Sean Gillies says:

    Fantastic. I’ve extracted the 1678 cross-references between Pleiades and Geonames and attached them in a JSON file to

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