It was once just a small hole in the ground, providing a minor inconvenience to local joggers and dog walkers coming to enjoy the views over the rugged cliffs.
But the once man-sized Souter Hole at Whitburn, near Sunderland, has now become a 40ft-wide awe-inspiring giant.
The massive 'sinkhole' first appeared as a small hole in the ground in 2003. But through erosion and landslips the natural phenomenon has grown and grown.
Now it is so big that a hidden beach has been carved out inside, with the sea forcing its way through a crack in one of the cliff walls.
Erosion and landslips have left a gaping hole on a field leading to the cliffs at Whitburn, near Sunderland
But the once man-sized Souter Hole at Whitburn, near Sunderland, has now become a 40ft-wide monster - and in doing so has revealed a secret
Beach artist Clair Eason, a former GP, captured the true extent of the sinkhole while exploring the coastline near her home.
She said: 'This deep sink hole near Souter Point, South Shields, began as a small hollow a few years ago.
'It's growing into a huge beast, adding even more drama to the rugged coastline.'
Experts say the giant sinkhole, also known in geological terms as a 'doline', most likely formed through sea water being pushed through a fault in the limestone cliffs.
However the British Geological Survey's Shallow Geohazards and Risks team leader, Vanessa Banks, said such sinkholes are not uncommon in coastal areas like Whitburn.
Ms Banks, who has studied geology for 40 years, told MailOnline: 'Dolines are often formed where you have cold water and glacial sand and gravel deposits underlined by permeable rocks
