On Wed, Mar 11, 2015 at 9:24 AM Markus Krötzsch <markus@semantic-mediawiki.org> wrote:

No, you are right: this is of course an issue in the completeness of our
data. If you zoom in to Europe, you can see that some countries have
costs full of lighthouses, while others seem to lack them almost
completely. I think it clearly shows that a lot of our data comes from
Wikipedias (in some specific language).

In this instance, the issue appears to be that the existing lists on Wikipedia have not been touched, e.g.:
https://en.wikipedia.org/wiki/List_of_lighthouses_in_Spain

These, including redlinks, could be imported into Wikidata rather easily. Some already have images.

Ideally, we'd want some "official" (e.g. national, UN) source to cross-check.