In 1930, when the Zion-Mt. Carmel Tunnel was completed in Zion National Park, it was the longest tunnel anywhere in America outside of an urban city. Today, this 1.1-mile tunnel navigates the innards of a soaring sandstone mountain, and provides a conduit connecting Zion National Park with Utah’s famous Bryce Canyon. The road itself, the Zion-Mt. Carmel Highway, is listed on the National Register of Historic Places for its beauty and feats of engineering—the grandest of which is the Zion-Mt. Carmel Tunnel that’s become an attraction in itself. As a means of illuminating the deeply dark tunnel, multiple “windows” have been cut through the wall to showcase the view outside, though you’ll want to keep moving, rather than stop, to make sure traffic keeps flowing. In the three years that it took to complete the Zion-Mt. Carmel Tunnel, the total cost eventually ballooned to just over half a million dollars. In 1930 that sum was unconscionable for simply creating a road, but seems like a bargain when you consider today the feat that the builders pulled off.