At first glance the rectangular island of Por-Bajin looks like a foreboding fortress or prison , with its regular structure and ruined sections . But it is unknown for certain what the rectangular island and its labyrinthine ruins , located in a lake in deepest Siberia , was actually used for when it was built 1,300 years ago . Historians and scientists are divided , but some experts believe the isolated area may have been built to attract people instead imprisoning them , and suggest it was a summer palace , monastery , or an astronomical observatory . The mysterious island , Por-Bajin , was found in the centre of a remote lake high in the mountains of southern Siberia . A reconstruction sought to show what the island could have looked like before it was ruined . The fortress is located about 3,800km from Moscow near the Mongolian border . The plot thickens as the way it was built , along with the construction materials use , hint at Chinese architectural tradition . The name Por-Bajin translates as 'clay house ' in the Tuvan language , and the island sits between the Sayan and Altai ranges , about 3,800km from Moscow near the Mongolian border . The location was first discovered in 1891 , and the purpose of island has still not been explained over a century later . More in-depth research took place in 2007 with archaeologists discovering clay tablets of human feet , faded coloured drawings on the plaster of the walls , giant gates and fragments of burnt wood . Experts say the island was built during the period of the Uighur Khaganate ( 744-840 AD ) but it is not clear what their motive would be for constructing a fortress for in such a solitary place – as it is far from big settlements and trade routes . Archaeologists conducted limited and inconclusive excavations at the site in the 1950s and 1960s . The ruined structures have led experts to believe the island was used as a fortress or prison . The island has baffled experts for over a hundred years who say it could have been anything from a prison , to a palace or monastry . The plot thickens as the way it was built , along with the construction materials use , hint at Chinese architectural tradition . Scientists were able to use laser mapping to create a 3D image of what the 3.5 hectare plot could have been used for . Although it is said to be around 1,300 years old , many walls were intact and well preserved with a main structure in the inner courtyard being separated into two parts , covered by a tiled roof walkway supported by 36 wooden columns on stone bases . Isolated ruins ! The fortress is connected to other land via a small walkway . Irina Arzhantseva of the Russian Academy of Sciences is now digging here for the Por-Bajin Cultural Foundation to find out just when the complex was built and why . Even more confusing than the debate of why it was created is the question of why it was abandoned . Researches have noted the lack of heating systems on the island , despite it enduring harsh Siberian weather and being located 7,545 feet above sea level . Russian president Vladimir Putin visited the island with Prince Albert of Monaco in 2007 and echoed the confusion . ' I have been to many places , I have seen many things , but I have never seen anything of the kind , ' he said . Por-Bajin ( 'clay House ' in the Tuvan language ) was long thought to be a fortress built by the Uighurs . The few artifacts unearthed at the site seem to date it to the mid-eighth century . A Chinese roof tile hints at Chinese influences , ( right ) . Russian president Vladimir Putin visited the island with Prince Albert of Monaco in 2007 and said : ' I have been to many places , I have seen many things , but I have never seen anything of the kind '
Researches was discovered a century ago and is still a mystery for experts . The 3.5 hectare site is located in a Siberian lake near the Mongolian border . The unexplained site is estimated to have been built between 744-840 AD .