Greg Girard Between the 1950s and 1994, tens of thousands of immigrants constructed a towering community 12 stories high across a 6.4-acre lot in Hong Kong.

It was called Kowloon Walled City.

With a population of 33,000 squeezed into the tiny lot, the city was 119 times denser at its peak than present-day New York City. Although it faced high levels of crime and poor sanitation, the city was also impressively self-sustainable — until its demolition in 1993.

In the late '80s, Canadian photographer Greg Girard found his way into the windowless world.

He shared some photos and thoughts on his time in Kowloon Walled City with us here. You can check out the rest of his photos together with essays and work from photographer Ian Lambot in the recently released book "City of Darkness: Revisited."