This fascinating visual from The Social Computing Group at MIT Media Lab called You Are Here relies on opening hours of Detroit businesses. By 8am the whole city seems to be awake and into the early hours of the night/morning there are only a handful of 24 hour businesses. There is obviously a lot of businesses focused Downtown, but I wonder how comprehensive their dataset is for smaller businesses outside of the Downtown/Midtown area?

They also did a cool thing where they paired down roads to the most active for businesses throughout the day.