This mysterious uninhabited island in Argentina’s swampy Paraná Delta, just outside Buenos Aires, first captured the attention of filmmakers due to its incredible circular shape - a floating island sat within a slightly larger circular lake.

       This bizarre landscape earned it the name of El Ojo - meaning “the eye”.

       The filmmakers, led by Argentinian director Sergio Neuspiller, first discovered the island after researching for a documentary on the river delta.

       "We found the perfect circle, as seen from the air," Mr Neuspiller told the newspaper El Observador in a translated article. "The water looked black but in reality it was completely transparent water, something that is almost impossible to find in the delta [because the waters are generally muddy], but it had a black earth bottom."

       What they then went on to discover made the discovery even more bizarre - the fact that it spins on its own axis - which has led people to believe that it harbours UFOs and the ghosts of ancient deities.

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       The island, which measures 118 metres by 120 metres in diameter, is made of aquatic plant matter and is believed to have existed since 2003. Typically, islands like these are loose and spongy, acting like a giant raft once the water gets too deep for the roots to attach.

       After looking at the island on Google Maps several times, Mr Neuspiller noticed a change in its position in the pond.

       While floating islands exist around the world, from Italy and Turkey to the US and the DRC, these islands do not rotate on their own axis.

       Some speculate that it may be similar to ice discs - almost perfect circles of ice on a river’s outer bend that spin on slow-moving currents and result from a force known as rotational shear.

       This occurs when current breaks off a piece of ice and rotates it, forcing the ice to grind against the bend and creating a circular shape. Ice discs can even rotate in still waters when changes in temperatures and density create a very gentle circular movement.

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       It is therefore possible that this chunk of land broke off and rotational sheer caused it to spin in a clockwise direction, grinding against the lake’s edge and smoothing it into an almost perfect circle.

       Some attribute the phenomenon to a natural well within the marshes, which would explain how the island moves so smoothly.

       While researching the region, the film crew discovered that local residents knew about El Ojo, but that some fear the island due to beliefs that an ancient deity lives there.

       Other theories about the island suggest it attracts UFOs and harbours a Nazi base, according to El Cronista, but there is no evidence to support these claims.

       To investigate the mystery more deeply, Neuspiller enlisted the help of an American engineer named Ricardo Petroni. The pair hoped to raise $50,000 (￡40,000) for research but were unable to reach their goal. As a result, much about El Ojo remains a mystery.