At first glance these ponds appear unremarkable, but the name and the aerial images hint at something much more interesting. They are actually sinkholes in the Magnesian Limestone
The holes are believed to have formed in an earthquake in 1179 and a huge amount of local folklore and legends have built up about site, which you can read on the ‘Old Corpse Road’ website. Links to Lewis Carols Alice in Wonderland have also been claimed as Charles Dodgson lived nearby as a child
The northern ‘Double Kettle’ is filled with water from surface run-off, however the water in the southern ‘Croft Kettle’ comes from subterranean springs, which is very noticeable on Google Earth imagery. The site is a SSSI as its the only place in Country Durham where this occurs.