An ice cave, which forms naturally on a high-altitude glacier in the Swiss Alps, was accessible this week, to the delight of nature lovers and photographers keen to enter the 'Ice Cathedral’, which varies each year. 

The bluish cave, with a rounded ceiling made of thick ice about five metres high, is about 20 metres long. 

The 'unique show' from inside the tunnel is accessible by foot in 15 minutes from the chairlift at Glacier 3000 above the resort of Les Diablerets - but at your own risk, organisers said. 

The natural cave, also known as 'The Mill', forms through a siphon effect. Each spring and summer, the cavity fills with water from the snow melt, forming a lake. In autumn, the plug disappears and the water drains, leaving the cave. 

"It's magnificent, but even that isn't the right word. I've never seen anything like it, almost as if it's not of this world in fact. It's magnificent, I can only recommend it if you have the chance to go," Helen Tromp, a Dutch woman living nearby said after visiting.

Brice Rozes, touring the site on his day off, said: "It's very impressive. The vault is incredible. Standing beneath it, you can just imagine the weight above. It's beautiful."