With the WeKnowIt Visual Retrieval and Localization web-based tool
(ViRaL) you can make queries with city photos, find similar ones and
identify them on the map. Using a large database of geo-tagged images
from Flickr™, ViRaL can match a given query and return a ranked list of
images according to visual similarity. The geo-tags of the returned
images are used to provide an estimate of the location of the query
photo and display it using Google Maps™. The most common tags of these
images are also shown, giving a hint of e.g. what landmark might be
depicted in the query.

The tool is available online at:
http://www.image.ntua.gr/iva/tools/viral