Marriott's ads will show the Eiffel Tower and the Colosseum in Rome projected across London's River Thames for three days from Thursday.
The technology, called ECHO, will be used commercially for the first time says outdoor agency Kinetic. The agency worked with technology company Lightvert on the campaign.
The technology uses the concept of "low attention processing," a model identified by academic Robert Heath in 2000 showing that advertising messages can work even if someone is not paying active attention to them.
The ads will be up in the sky but the public won't be directly looking at them. How, then, does it make sense? There is a way. And there will be more to come.