<http://schema.org/keywords>
"park, sunrise, city, river, night, clouds, bridge, love, skate, lisbon, portugal, sigma 10-20, sin, canon 550d, dark sky, tagus"^^<http://www.w3.org/2001/XMLSchema#string>
<https://marketplace.500px.com/photos/19902421/sin-city-by-nuno-mota>