Last year, the world’s population reached 7 billion people. Because of our continually accelerating population growth, we keep hearing that more and more people will end up living in cities (and mega cities). But what’s that really look like? How will the world change?

Unicef, with the help of design studio Periscopic, released “An Urban World” to answer these questions. It’s an interactive, HTML5 visualization of the world from the years 1950-2050. But rather than showing our geographic boundaries, every country* is depicted only by their population living in urban environments.

As urban populations grow, the circles get bigger. And as urban populations get more dense, the circles shift from green to blue to yellow to some dark pink color (that I refuse to name with more specificity because it will only stir a debate**).

Once you get over the fact that, by 2050, both China and India will have about a billion people living in cities alone, you can mine the image for thoughtful comparison. For instance, since the 1990s, more than 75% of the U.S. population has lived in cities. We were once an outlier in this regard, but found ourselves joined over the next two decades by France, Spain, the U.K., Mexico, Korea, Australia, and Brazil.

Yet China and India swell to astounding proportions without reaching our general city density. By 2050, somewhere between 50-75% of their population will live in cities. In other words, the India and China of tomorrow look a lot like the U.S. from the 1980s.

Now, whether this ends up being a good or bad thing–whether we’re talking about urban slums or smartly scaled communities, loosely populated expanses of efficient agriculture, or underdeveloped countrysides stricken by poverty–none of that is written on this map because none of that is written just yet. But it’s hard to watch these bubbles grow, expanding into one another in a battle for your mere vision (let alone food, housing, and wages) and earnestly expect that everything is just going to be all right.

That said, there are complex dynamics related to cities and innovation, which also might define the course of sustainability, albeit in a looser way. Studies have shown that people living in cities tend to be far more energy efficient. But that energy surplus is usually directed toward more and more growth, meaning that cities don’t improve our carbon footprints. Think about it: What you save in not owning a car is probably spent on a thousand other things that take energy to produce.