The most comprehensive picture of what goes on inside the secret state of North Korea has emerged from an innovative US project. The location of extraordinary palaces, labour camps and the mass graves of famine victims have all been identified. The online operation that has penetrated the world's last remaining iron curtain is called North Korea Uncovered. Founded by Curtis Melvin, a postgraduate student at George Mason University, Virginia, it uses Google Earth, photographs, academic and specialist reports and a global network of contributors who have visited or studied the country. Mr Melvin says the collaborative project is an example of "democratised intelligence". He is the first to emphasise that the picture is far from complete, but it is, until the country opens up, the best we have.

Palaces

The palatial residences of the political elite are easy to identify as they are in sharp contrast to the majority of housing in the deeply impoverished state. Though details about many palaces' names, occupants and uses are hard to verify, it is known that such buildings are the exclusive domain of Kim Jong-Il, his family and his top political aides. Kim Jong-Il is believed to have between 10 and 17 palaces, many of which have been spotted on Google Earth:

Download the new Independent Premium app Sharing the full story, not just the headlines

1) Mansion complex near Pyongyang

This may be Kim Jong-Il's main residence. His father lived here surrounded by the huge, ornate gardens and carefully designed network of lakes. Tree-lined paths lead to a swimming pool with a huge water slide, and next to the complex there is a full-size racetrack with a viewing stand and arena. There is a cluster of other large houses around the mansion, forming an enclosed, elite community. It appears to be reached via an underground station on a private railway which branches off from the main line.

2) Kangdong estate

This lies about 18 miles north-east of Pyongyang and has an elaborate garden, set around many lakes. There are numerous guest houses, and a banqueting hall, within the security-fenced perimeter. Kenji Fujimoto, who served as Kim Jong-Il's cook from 1988 until 2001, said entertainment at Kangdong included bowling, shooting and roller-skating. There is also a racetrack next to the complex and Kangdong airfield is just 2.5 miles away.

3) Unnamed palace on the banks of the Changsuwon lake

The residence sits across the lake from a couple of other mansions which may house relatives of the current occupant. One Google Earth tag suggested that this might be the home of Kim Yong Nam, the second-in-command in North Korea's leadership.

4) Jungbangsan or Hwangju palace

An enormous mountain retreat set in manicured gardens with lakes and winding paths. It allegedly has several entrances to an underground facility within the steep hill next to the mansion. Google Earth reveals a railway track which runs along the top of the hill then disappears mysteriously into its east side.

5) Nampo Mansion

Estate covering a huge area with an unusual chain of dammed lakes. There are many buildings making up the mansion compound, which probably cater for members of the North Korean leadership.

6) Yongpong Mansion

Kim Jong-Il's residence on the banks of Lake Yongpong, near the city of Anju, which he uses as a private hunting retreat. According to one defector, Han Young Jin, writing in 2005, it is known for its lakeside fishing spots and hunting ground, which was completed in 1984. The mansion was originally further south and was moved after an enlargement in 1979. The estate contains the main house and 10 security and support facility buildings.

7) The Wonsan Palace

One of Kim Jong-Il's favourite holiday destinations, sitting on a peninsula lined with white sand beaches. Wonsan is where Kim Jong-Il and his relatives enjoy fishing, hunting guillemots, jetskiing and swimming during the winter. Lee Young Kuk, who worked as one of Kim Jong-Il's guards from 1979 to 1988, claimed that Kim also spent time at Wonsan hunting roe deer, pheasants and wild geese. The palace is conveniently next door to an airfield. Kim Jong-Il's enormous private yacht was caught by satellite image at anchor up the coast in Wonsan harbour. On board the vessel there is a 50-metre pool with two water slides.

8) The Hyangsan Chalet

Daily coronavirus briefing No hype, just the advice and analysis you need Enter your email address Continue Continue Please enter an email address Email address is invalid Fill out this field Email address is invalid Email already exists. Log in to update your newsletter preferences Register with your social account or click here to log in I would like to receive morning headlines Monday - Friday plus breaking news alerts by email Update newsletter preferences

Large mountain retreat, located on the Horang ridge at an altitude of about 1,000m. Han Young Jin described it as a traditional Korean-style building, completed in 1984, with beautiful views of the Myohyang mountains. The compound contains three buildings for security and support facilities, and there are reports of several entrances to an underground facility beneath Hyangsan. The chalet allegedly is where Kim Il-Sung died.

Gulag-style prison camps

North Korean prison camps are split into two main types. Firstly the kwan li-so, translated as "political penal-labour colonies". These camps contain the political prisoners, and often their families, who are imprisoned without trial, usually for life. Sentences involve slave labour within the camps. The other type of camp, the kyo-hwa-so, are smaller penal-labour camps. These usually hold criminal offenders who are subject to a judicial process and fixed sentencing, after which they can be released. Kyo-hwa-so prisoners are also forced to do hard labour in mining, logging, textile manufacturing and more.

A US Human Rights Committee report in 2006 asserted that there were more than 200,000 prisoners throughout North Korea, a figure that may now have risen to 300,000. Estimates claim more than 400,000 have died in the system in 30 years. What little is known about these camps comes mainly from the testimonies of ex-detainees and ex-prison guards. Most of their accounts date back to the 1980s and 1990s and little new evidence has since come to light.

1) Kyo-hwa-so 1

A labour camp in Gaechun, South Pyongan province. Lee Soon Ok, who was imprisoned here until 1994, described prisoners dying from torture and maltreatment, their bodies dumped on the mountainsides "like animals". At the time of her imprisonment from 1986, around 6,000 people were held within the camp's high walls and electric fences, and its main industries were clothes and shoe manufacturing.

2) Kwan-li-so 14

This is near Kaechon, South Pyongan province, on the north bank of the Taedong River opposite camp 18. It measures 25 to 31 miles by 19 miles, and contains about 15,000 prisoners, according to Kim Yong, who was held there from 1995-96. Kim said the main industries were mining and farming and that many people died due to malnutrition, disease and mining accidents.

3) Kwan-li-so 15

This is located at Yodok in South Hamgyong province. Descriptions of the camp by refugees cover all the years from 1977 to 1999. These include Kang Chol Hwan, the author of Aquariums of Pyongyang: Ten Years in the North Korean Gulag, whose small village within camp 15 suffered about 100 deaths every year due to malnutrition and disease. In the 1990s Yodok held more than 45,000 prisoners, surrounded by a barbed-wire fence up to 4m high and walls topped with electric wires. Along the fence were watchtowers patrolled by guards carrying automatic rifles and hand grenades. In the camp there was a gypsum quarry, textile plants, distilleries and a gold mine, where there were frequent accidents. Lee Young Kuk, a prisoner until 1999, witnessed numerous public executions and shootings in the camp.

4) Kwan li-so 16

Less is known about this camp at Hwasong, North Hamgyong province than the others. This could be because it lies adjacent to another highly secret location, the Mount Mantap nuclear testing site, and it is close to the Musudan-ri missile-testing facility. The camp measures 18 miles by 16 miles and is believed to hold 10,000 prisoners.

5) Kwan li-so 18

This camp lies at Bukchang on the south bank of the Taedong River, South Pyongan province. Kim Yong, who was transferred here in 1996 and escaped in 1998, said it held approximately 50,000 people, mainly the families of those imprisoned in camp 14. Bukchang was less severe than camp 14, but Kim Yong still witnessed prisoners dying of malnutrition and being shot. The main industries were coal mining, brick making and cement making.

6) Kwan li-so 22

Camp located at Hoeryong in North Hamgyong province, the north-eastern tip of the country. Former guard Ahn Myong Chol described it as one of the largest prison camps, containing around 50,000 prisoners within an area 31 miles long by 25 miles wide. Hoeryong is infamous for reports of chemical weapons experiments on humans, and glass gas chambers, revealed in a BBC documentary Axis of Evil in 2004.

Mass graves

North Korea was hit by a famine in the 1990s that killed a huge number of its people. Estimates of the death toll between 1995 and 1998 vary from 600,000 to 3.5 million from a population of 22 million. The US State Department claims two million died of starvation in these years. While thousands starved, particularly in the north-east, the regime continued to prioritise weapons buying and sent shipments of international aid to politically favoured areas on the west coast.

1) Hamhung mass graves

Hamhung city in South Hamgyong province was among the worst affected by famine. In 1998 a former engineering student told Kyodo News Services that more than 10 per cent of the city's population, including his mother, had starved to death, while another 10 per cent fled the city to find food. Google Earth images have revealed mass graves on the hills around the city of Hamhung. One can see a multitude of distinctive mounds packed on to the slopes. The graves begin within a well-organised cemetery then spread. The small mounds consume the entire hill, the hills around it and nearly all the unoccupied land surrounding the city. One North Korea Uncovered researcher, Joshua Stanton, believes the number of graves exceeds 100,000, and if the smaller and less dense burial areas are included, the total could be twice that figure.

2) Unnamed graves

This is another burial ground just east of the capital, Pyongyang, where the small mounds are again visible on the hillsides. There are other large, haphazard burial grounds in North Korea. No date or cause of death relating to these graves can be determined from the satellite images. But most commentators agree it is unlikely that normal circumstances could produce such a great density of burials. The concentration of graves would be consistent with published reports filed from Hamhung during the famine.