A lot of people are linking to the Times Square lego x-wing today. Well, right near my home town is a museum that claims “largest permanent LEGO® installation at minifigure scale in the world” at 3 million bricks. It’s a replica of downtown Manchester, NH in its heyday about 100 years ago. It’s spectacular and you can easily spend an hour or two spotting all the details.
http://www.see-sciencecenter.org/visitors/millyard-project.aspx