Mapping between Wikidata and Geonames

Question

Where can I find a mapping between Wikidata entities and Geonames entities?

Wikidata: GeoNames:

Answer 1

Approximately since October 2014 there exists GeoNames ID external identifier on Wikidata. The current number of entities with this identifier is about 1 500 000.

You could retrive this identifier value for Antananarivo using the following SPARQL query:

SELECT ?geoNamesID WHERE
{
   ?place wdt:P1566 ?geoNamesID 
   VALUES (?place) {(wd:Q3915)}
}

Try it.

Answer 2

The Geonames RDF for Antananarivo links to Wikipedia:

<gn:wikipediaArticle rdf:resource="http://en.wikipedia.org/wiki/Antananarivo"/>

You should be able to use that to get the corresponding Wikidata entity.