- Kowloon Walled City was once considered the densest settlement on earth
- 33,000 people lived within the space of one city block, with little government regulation
- Photographer Greg Girard spent years documenting the Walled City before its demolition
(CNN)Picture a colossal empire of little houses stacked on top of each other. Visualize them connected by staircases snaking under dangling wires, through corridors so dark even police were rumored to be afraid of them.