<http://schema.org/keywords>
"sunrise, fog, nebel, wolken, sonnenaufgang, tree, baum, Donau, Fluss, Wallsee, river, clouds, danube, Wasser, sky, water"^^<http://www.w3.org/2001/XMLSchema#string>
<https://marketplace.500px.com/photos/6421243/wallsee-by-leo-p%25C3%25B6cksteiner>