UPDATED ANSWER:
Wikilocation has been retired and now there is an OFFICIAL WIKIPEDIA API
? action=query
& list=geosearch
& gsradius=<radius-in-meters>
& gscoord=<lat>|<lon>
HTML example | JSON Example
UPDATED ANSWER:
Wikilocation has been retired and now there is an OFFICIAL WIKIPEDIA API
? action=query
& list=geosearch
& gsradius=<radius-in-meters>
& gscoord=<lat>|<lon>
HTML example | JSON Example