While it may look like a natural phenomenon, this watery sinkhole is anything but.

Named Covão do Conchos it is regarded as one of Portugal’s top secret attractions.

The mesmerising whirlpool, which has been caught in high definition by a circling drone, is the work of human engineering and can be found in an otherwise tranquil lake in Serra da Estrela Natural Park.

People say the opening in Portugal’s largest protected area looks like it’s from an otherworldly dimension. However, it is far less mystical and far more fascinating.

In the middle of the lake is an opening of 4.6 meters with a circumference of 48 meters through which water free falls into a dam.

The water pools down a 1500-metre long tunnel to the Lagoa Comprida hydro-electric dam.

The system, which can be seen whirling away in a video on Daniel Alvez and Hélder Tavares’s YouTube channel ProBilder, was built in 1955.

In the last 60 years, nature has found life on the mouth of the funnel with moss and foliage growing at the edges.

While its location in the Serra de Estrela mountain range is remote it has become a popular hiking hotspot.

However, tourists are warned it can be a treacherous path and are recommended to wear waterproof walking shows and weather-resistant clothing and thermals as temperatures are likely to be cold.

Winter weather can be particularly testing as the area becomes blanketed in snow and ice.