Back in 2007, one of the teams at Yahoo Research Berkeley (YRB) built an awesome tool on top of Flickr that showed on a map the things that were photographed somewhat, but not a ton.

For instance, it wouldn't surface pictures of the Golden Gate Bridge, but it did show pictures of the Yoda statue in the Presidio (how I learned of it's existence). There was even day mode and night mode to see what was interesting, but not well known, at different times.

Perhaps unsurprisingly, it never found its way to actual release, but it taught me a ton about where to look in data for the cool bits of info.