Over the summer, he kept returning to the cave to marvel at the dance of the shadows on the walls.

NEWYORKER: Master of Play

But normally, save for the odd urban explorer or raver illegally slipping onto the tracks for a nose around or a dance, this eerie world of shadows and ghosts has been all but forgotten.

BBC: Reawakening the Underground

Nameless waterfalls tumble down from the plateau above, while the shadows of clouds dance across treeless slopes.

BBC: An Icelandic journey to the centre of the earth