But walk through the doors, down a narrow stairway and through a winding tunnel to the main room with its bare cement walls and smell of mould, and it's clear this is a night club like no other in this trendy Chinese city.

For The Shelter is one of a handful of former bomb shelters finding new life as commercial venues, ranging from clubs to clothing shops and even wine sellers.

"It is gloomy and clammy, and very unique," said Kis Chen, a 29-year-old office worker who hunts around town for exotic clubbing scenes.

"The smell reminds me of my childhood home," she added, referring to the musty smell of clothes and furniture familiar to many Shanghai residents during the summer rainy season.

Hundreds of thousands of bomb shelters were built across China in the 1960s and 1970s to prepare for possible air raids from the then-Soviet Union amidst a souring relationship between the two communist countries.

It's unclear how many of the underground shelters were built in Shanghai. But the local government says there are about 2,000 in the Xuhui district, a mix of commercial buildings and the elegance of the old French concession, where The Shelter is located.

"Some projects remain as secrets," said Tong Songyan, an official at the Xuhui district government, when asked how extensive the bomb shelter network was.

The shelters were let out by the government after tensions with the Soviet Union eased in the mid 1970s. There is no specific figure on how many have been converted, but it may be only a small fraction of the total.

For many such places, the unusual structure of the shelters - as well as their underground location - is used to good advantage.

One is MANifesto, which sells underwear exclusively for men. Conveniently located next to an underground gay bar called Shanghai Studio, shoppers say the secretive location offers an extra "sense of safety" for customers wary of being seen.

And at wine seller Ruby Red, marketing manager Flora Wang says the naturally cool temperature is perfect.

"Our clients think this bomb-shelter structure is very professional," she said, in the 600-square-meter (yard) cellar filled will wooden boxes from floor to ceiling.

The Shelter went through incarnations as a vegetable market, ice storage facility, massage parlour and even a public bath house before taking on its current form as a night club in 2007.

Despite its mouldy smell and occasional flooding during heavy rain the 600-square-meter, The Shelter has become one of the more popular venues among the clubbing set, featuring things such as reggae, drum and bass, and soul.

Playing up its windowless nature to the hilt, the club sometimes throws "pitch-dark" parties, shutting down all the lights and even Wi-Fi connections, leaving only the music on.

"It is different from all the other commercial bars in Shanghai. The music is very good and my friends like it," said Brett Simons, a 28-year-old software engineer from Australia.

"This underground place is quite cool."

(Reporting By Shanghai Newsroom; Editing by Kazunori Takada and Elaine Lies)

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