You get Wikipedia results like http://maps/wikipedia_51.2736_30.2264.html Notice that since there is a previous "http://" it is interpreted as an absolute linke instead of relative. It goes to wherever your browser takes broken links.
I have now also added the alternate name 'Chernobil' to the geonames database. The result returned by the query above will thus be a geonames listing and no longer a wikipedia one.