Mitholz - the tranquil Swiss village facing a time bomb

Mitholz, population just 170, is at first sight an idyllic place in Switzerland's beautiful Kander Valley. But its tragic history has come back to haunt it.

The village's geranium-covered houses are traditional wooden farming chalets, many still with living space for people upstairs, and stalls for farm animals below.

It's a style seen all over the Alps, with some houses 200 or 300 years old. But not in Mitholz. Here all the houses bear the same date: 1948.

Some have inscriptions: "Out of the horror, I am rebuilt" or "What was destroyed in a moment cannot come back. Now we look forward with hope."

What happened? Halfway along Mitholz's single street Ida Steiner remembers.

"I was 12," she says. "I, my mother and my grandmother were asleep. There was a huge explosion, we saw fire everywhere, and mum said: 'We've got to get out!'

"We ran out into the night, there was deep snow. My mother carried my grandma on her back."