An estimated 1 million people came to Downtown and Over-the-Rhine over four days ending on Sunday for the first-ever Blink Cincinnati festival, the Cincinnati Enquirer reports.

The festival offered projection mapping on the sides of buildings and other surfaces, murals, urban artscapes and interactive art across 20 blocks from the banks of the Ohio River to Findlay Market.

The Cincinnati USA Regional Chamber, which handled the logistics for the event, said it was the largest single event the city has ever hosted. The event's organizers estimated Blink cost about $3M to stage.

Blink is a recent example of what The New York Times calls "Art on the Outside." Besides offering outdoor art, events of this kind draw attention to their neighborhoods and contribute to placemaking through word-of-mouth and social media.

During its run, Blink was featured in more than 1,500 tweets and 7,000 Instagram posts, the event's organizers said.

Outdoor art and light shows are not new, but modern technology allows projection techniques that display images and animation on any kind of surface, not just flat or white ones. Such projection was in full use during the Blink festival.

“The Cincinnati region, as well as visitors from around the nation and the globe, have embraced Blink in a big way,” said Tim Maloney, the founder of  Blink and president and CEO of the Carol Ann and Ralph V. Haile Jr. U.S. Bank Foundation.