Even on a quiet day the British Museum in London is full, but on a rainy day during the summer it is positively packed, with a long line of visitors winding around the corner. Adding to the popularity at the moment is an exhibit on two mystical sunken cities that were discovered fairly recently and are still being studied by a team of underwater archeologists.

The two lost cities were Canopus and Thonis-Heraclion , bustling social centers at their time and important places of trade in the Mediterranean. As I wandered through the exhibit of marvelous artifacts from a rare blend of Egyptian and Greek culture I wondered why two well-organized and powerful port cities literally vanished into the ocean and drowned. Why did the people who created those cities abandon the treasures on display at the exhibit?

Of course my first association was with sea level rise—and I felt a stinging sense of irony, because the exhibit is sponsored by BP. But it turns out that the explanation is not quite so simple.

Canopus and Thonis-Heraclion most likely drowned because they were poorly designed. The ground they were built on was soft and gave way, much like one of the main factors contributing to the sinking of modern Venice. Apparently earthquakes and tsunamis contributed to the final decision to abandon the cities – although that is mainly speculation.¹

But in the end, does it matter if the sea is rising due to melting ice caps or if your city is sinking into the muddy ground? Of course Venice is a great example of a place that is battling this now on both fronts: sea-level rise and a soft underground. So far human engineering has maintained Venice, and there are plans to protect it into the future. But there is clearly no guarantee that this beautiful city will survive in the long term. This raises a much more general question: as we face projected sea-level rises of up to 4 feet by 2100. how much can we depend on technical solutions?

Some countries have the needed technology and experience to protect their cities—like the Netherlands. But other countries are far too poor to deploy the available technology. This, obviously, raises the issue of social justice. Is it ethical to let some areas drown, just because they don’t have the means to deal with rising sea levels? Interestingly, even in the very wealthy USA it has been quietly accepted that not all coastal communities can be saved. I think that recent storms like Katrina or Sandy have forced this realization on people in Louisiana and New York.

But there is something else this exhibit made me think about, namely that there is a way to see as cities the ultimate version of human niche construction. Urbanization is currently one of the most important trends of human life. Modern cities allow humans to live in extremely high densities, and require an extreme degree of division of labor and specialization. They create a unique habitat not just for humans, but also for the animals, plants, and microbes that colonize cities. Cities even have their own microclimate.

It is very thought provoking to consider whether—or not—cities are superior to other forms of human settlement. On the one hand, obviously the formation of cities is a remarkable landmark for most human cultures that was reached several times independently. Furthermore, cities and their functions have changed many times in history. Maybe they started out as defensive structures, but today they are clearly hubs for fast and easy access to services.

On the other hand, the downside of urban life may be equally fast spread of diseases. And again the question of social justice becomes relevant. While Rio de Janeiro—now in the spotlight with the Olympic Games—may be a great place for some people, there are some obviously many disenfranchised people stuck in favelas, where they receive only a fraction of the services the majority of the other inhabitants take for granted.

But if we want to consider whether cities are the pinnacle of human habitation I think we must also wonder, what makes a good city, what a bad one? There are countless questions to be explored here. Can we even compare ancient cities like the two sunken cities on exhibit in the British Museum with present day London, New York, or Tokyo?

All of this was on my mind as I marveled at the items on display in the sunken cities exhibit. The items on display ranged from mundane household items to religious objects, but to me the most impressive objects were statues of a ruling couple, approximately 5 meters high, at the same time imposing and beautiful. Yet in creating monuments to all this wealth and vigor, how did the—obviously talented—engineers not realize they were building on soft ground, thereby dooming the cities?

Whatever the explanation, the sunken cities of Canopus and Thonis-Heraclion must be viewed as failed attempts to create human habitation. How did this happen? What were the political and social consequences of the failure? What became of their occupants who had to flee their homes? Did they lose everything but their lives?

Leaving the exhibit I caught myself wondering if in a hundred or a thousand years someone will put on an exhibit illuminating the fate of coastal dwellings in Hamburg, Miami, New Orleans, or Manhattan?

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