A Room for London, a one-bedroom pop-up hotel in the shape of a small boat which looks as if it has been washed up on top of the Southbank Centre's Queen Elizabeth Hall, gives up to two people a night the opportunity to experience such unique views of the capital.

"To have that 18 hours on your own in central London is quite a privilege in lots of ways," said Mark Robinson, director of Living Architecture, a not-for-profit company which aims to promote the appreciation of modern architecture through building unique houses for holiday rental around Britain.

"Watching that cycle of London through the day ... you notice how the city moves," he told Reuters.

The room is reached via a temporary lift, which crawls up the outside of the building at a snail's pace due to concerns the noise of any greater speed would disrupt the concerts on the other side of the 1960s concrete wall.

Having made their way across the bleak grey roof on a scaffold walkway and wiped their feet on the welcome mat outside the front door, visitors are given a short safety briefing before being left to their own devices.

Inside, the boat is unexpectedly large and while far from seaworthy, everything from its timber-lined walls down to the tidal tables and log book help give it an authentic feel.

Through a porthole in the bathroom, visitors can look out over the London Eye as they brush their teeth, while a corresponding window on the opposite side of the boat gives occupants a clear view of the Shard skyscraper from the shower.

A screen separates a small kitchen area from the spacious bedroom-cum-lounge beyond, where visitors can sit on a semi-circular window seat and take in the world below using the binoculars provided or browse one of the many books on London's history dotted around the cabin.

From a hatch in the ceiling, a pulldown ladder provides access to an octagonal library room above. A door off the library takes visitors out on to a large balcony overlooking the Thames where Big Ben's hourly chimes can be heard over the sound of trains chugging across the bridge into Charing Cross station.

HEART OF DARKNESS

The project is Living Architecture's fifth, and most temporary, creation since it was set up in 2007.

It follows an increasingly popular trend for temporary alternative uses of spaces, which has seen everything from pop-up shops and restaurants to cinemas and museums open in a location for a period of days or months before moving elsewhere.

After months spent researching the best location along the river to site it, Living Architecture and arts organisation Artangel ran a competition to design the structure. They received more than 500 ideas from around the world, including a semi-translucent moon-like sphere which lit up at night.

"There were lots of different shapes, boxes, towers, things that hung over the edge of the roof," Robinson said.

The winning entry, designed by David Kohn Architects and artist Fiona Banner, was inspired by the Roi des Belges, a riverboat captained by Polish author Joseph Conrad in the Congo -- a journey later echoed in his book "Heart of Darkness".

"We chose it because of the narrative ... and the connection with literature and art," said Robinson.

The boat, which took a year to develop and build, is in place for the whole of 2012, with the last week of every month set aside for an arts programme of writings, readings and live music created in A Room for London and produced by Artangel.

While the whole project cost more than half a million pounds, the room comes with a reasonable price tag as Living Architecture charges visitors to its creations only what is needed to cover the running costs, meeting capital costs from philanthropic donations.

At around 150 pounds for two people for a night it is a fraction of the cost of a room with a similar view in the luxurious Savoy hotel opposite.

"We wanted to be accessible ultimately, it wasn't seen to be exclusive, that is the last thing we wanted," said Robinson, adding that the majority of visitors so far have been London based. "It seemed to capture Londoners' imagination."

But having sold out within minutes, others keen to set sail in the Roi des Belges will have to await its next location.

"It could go anywhere now. It could go on to a another building or in the middle of a field," said Robinson. "It is dismountable so we will pick it up put it on the back of a truck and take it somewhere else."

(Reporting by Kylie MacLellan, editing by Paul Casciato)

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