Kowloon Walled City was located in Kowloon City, Hong Kong, and it spans just 6.4 acres. At its peak, it was estimated to have 50,000 residents giving it a population density almost 120 times greater than New York City.

It was known for its interconnected high-rises and as being a crime haven since it was left alone by authorities. But there’s a lot more to the story behind the Walled City. So, here are 11 facts about the world’s most densely populated place.

1 The Walled City was originally a small fort built during the Song dynasty (960-1279). It then sat untouched for hundreds of years and was later converted into a military outpost with a defensive wall.

During the Qing dynasty (1644 to 1912), authorities wanted to use the fort as a military outpost to help check British influence. So, the fort was improved in 1847 with the addition of a defensive wall. After the Qing dynasty ended its rule, the British claimed ownership of the Walled City but didn’t do anything with it. It was mainly a tourist attraction, and on a map from 1915, it was labeled as “Chinese Town.” In the 1930s, there were about 400 squatters living there when Hong Kong authorities moved them out and demolished the decaying buildings.(1,2,3)

2 During WWII, the area was occupied by Japanese forces. They dismantled the defensive wall and used the materials to expand a nearby airport. After Japan’s surrender in 1945, people started moving back into the Walled City. There were 2,000 squatters living there by 1947. They included refugees and people attracted by the lack of laws.

Many of the squatters were refugees from the Chinese Civil War who wanted to get away from mainland China. As the population in the Walled City grew, in 1948 the British tried to drive the squatters out but failed. After that, they adopted a “hands-off” policy towards the Walled City.

With no health and safety regulations in the city, some businesses, such as food producers, began moving in to take advantage of the lack of rules.(1,2)

3 As the city’s population grew, people kept building on top of existing structures. The city eventually had 300 interconnected, high-rise buildings that had been constructed room-by-room without the help of architects or building codes. It became so dense that sunlight couldn’t reach the lower levels.

On the lower levels, it was permanently dark, so many alleys had fluorescent lights that were always on. People would carry umbrellas when using the alleys because there was a maze of overhead pipes everywhere, and they were constantly leaking. Many apartments had no windows or access to fresh air because they were enclosed within the middle of the buildings. The high-rises were so interconnected that you could travel from one side of the city to the other without touching the ground, instead, just passing through the corridors and across the rooftops.

One of the few rules enforced in the city was that no building could be higher than 14 stories. That’s because the Walled City was located so close to the airport that if the buildings were any taller they would’ve blocked the flight path of low-flying airplanes.(1,2,3)

4 Some residents living on the upper levels considered the rooftop as a sanctuary, as it was the only escape from the claustrophobia of the city.

Rooftops were often used for exercise and as playgrounds. They were also used for pigeon racing which residents gambled on like horse races. But the rooftops could also be dangerous, as there were some small gaps between the buildings. Also, due to lack of garbage collection, some residents carried their bulky junk items to the roof. As a result, many of the rooftops were cluttered with discarded mattresses, broken furniture, and appliances.(1,2)

5 Starting in the 1950s as the population grew and authorities kept their distance, the Walled City became a haven for crime. It was controlled by the Triads and was home to many brothels, opium dens, and gambling parlors.

Since the government had decided to leave the Walled City alone, laws typically weren’t enforced there. One reason it had been left alone was an old treaty that said the area would be left under the control of mainland China. But, in 1959, during a murder trial, a judge ruled that the Hong Kong government had jurisdiction there. By that point, crime in the city was so bad that police would only venture inside in large groups. Reportedly, many police officers still turned a blind eye to activities in the city, either as the result of bribes or just because it was too dangerous. So the crime continued mostly unchecked for years. But all that changed in the 1970s.(1,2)

6 In 1973-74, police carried out over 3,500 raids in the Walled City and seized more than 4,000 pounds of drugs.

In the 1970s, there were anti-corruption campaigns that removed the criminal elements in the police and weakened the Triads. After that, police launched a massive series of raids and arrested more than 2,500 people. Most of the city’s residents supported the police, and the raids continued over the years and made a significant impact. In 1983, police announced that the crime rate in the Walled City was under control.(1,2)

7 Despite high crime rates in the city, most residents were ordinary, law-abiding citizens. Many of them got involved in community groups to try to improve life in the Walled City.

There were a variety of legitimate businesses and institutions in the city. Interestingly, many of them had to share space. For instance, there were schools and hair salons that were converted into strip clubs and gambling halls at night.

One of the ways residents cooperated to improve the city was by creating a working water system. They worked together to dig wells and build thousands of pipes that wound through the buildings. Pumping the water required a lot of electricity, and residents took turns conserving power so that the water could be shared successfully. The Triads also worked with residents and acted as a kind of city council as they settled disputes between businesses, organized a garbage disposal system, and created a volunteer fire department.(1,2,3)

8 In the 1980’s, both the British and Chinese governments wanted the city to be demolished. So, they gave $350 million in compensation to residents and businesses and kicked them out of the city.

Authorities said they were concerned with the quality of life in the city, especially the poor sanitary conditions. So, in 1987, they announced their plans to demolish it. Some of the residents weren’t satisfied with the compensation and had to be forcibly evicted. After the residents found new homes, many of them said they considered their experience living in the Walled City as a happier time.(1,2)

9 In 1993, the city was demolished and turned into a park.

It’s now called Kowloon Walled City Park, and it’s popular among tourists and birdwatchers. Preserved in the park are some artifacts from the Walled City such as remnants of the South Gate that acted as the city’s main entrance. Also preserved there is the old administrative office that dates from the Qing dynasty and was later used to house seniors. The park also has a museum in honor of the Walled City.(1,2)

10 Some argue that the Walled City was an example of how people can work together to achieve great things. They say the residents came up with novel solutions to problems and created a city that was self-sufficient without needing guidance or an overall plan.

When the Walled City was being demolished, an architect named Aaron Tan who was a graduate student at the time, wrote his thesis on it. He said the Walled City had been like a machine that worked very well, and the demolition was like taking the machine apart and seeing how it works.

“It was a really humbling process for me as a designer — when we met this Walled City, we started to see that people could be more intelligent than us, the designers — that they could think of ways to solve problems that are outside the traditional academic world.”

A photographer named Greg Girard who chronicled the city said “You don’t want to romanticize a slum, you know. Because it was that. But it was much more than that. The Walled City was a kind of architectural touchstone in terms of what a city can be — unplanned, self-generated, unregulated.”(source)

11 Depictions of the Walled City have appeared in a variety of pop culture media from Batman Begins to Call of Duty: Black Ops. For a Jackie Chan movie, filmmakers set off explosions in one of the city’s abandoned buildings.

For the Jackie Chan movie Crime Story released in 1993, some scenes were filmed in the Walled City. During the film’s climax, one of the buildings in the city is wracked with explosions. At the time of filming, the city was already scheduled for demolition and the residents had either left or been evicted.

Other examples of pop culture depictions of the city include the movie Bloodsport as it features a martial arts tournament that takes place there. Also, in Batman Begins, there’s a dilapidated neighborhood in Gotham called “The Narrows” which is based on the Walled City.

The city has also been featured in a range of video games including Call of Duty: Black Ops, Hitman, Shenmue II, and Kowloon’s Gate. There’s also a game currently in development called HK Project where players control a cat as it explores the Walled City.(1,2,3,4,5)