Cities can make us sick due to the easy spread of diseases, and have also been demonized as breeding grounds for vice and crime. But cities have flourished nonetheless because they are humanity's greatest invention, indispensable engines for creativity, innovation, wealth, and civilization itself. However, during the global COVID crisis, the normal forms of socializing ground to a halt. How permanent are these changes? Do advances in technology mean that many people can opt out of city life as never before? Are we on the brink of a post-urban world? Edward Glaeser and David Cutler argue that a wave of urban failure would be absolutely disastrous. In terms of intimacy and inspiration, nothing can replace what cities offer. But great cities have always demanded great management, and our current crisis has exposed fearful gaps in our capacity for good governance. Deep inequities in health care and education are a particular blight on the future of our cities; solving them will be the difference between our collective good health and a downward spiral to a much darker place.