GENEVA, April 14 -- In most places, a night at the opera conjures up images of polite audiences in eveningwear sitting upright to enjoy a bit of Bel Canto.

In Geneva, though, once a year the crowd includes children, the eveningwear is pyjamas and socks - and the seats are scoped out for how comfortable they are to sleep in.

Welcome to Sleepover in the city's 19th-century opera house, when it opens its doors to a small number of enthusiasts.

From 8pm they wander its fresco-covered foyers, listen to performed music... and spend the night dozing in an auditorium lit up like a starry night.

"It's pretty crazy," said law professor Carine Lutz, as a friend next to her rolled out a sleeping bag at the foot of the stage.

They were among 180 ...