It has taken over a decade of painstaking work, but the structure of the world's first quarry hotel is now complete, with the property set to open in Shanghai next year, the owner has announced.
The Sheshan Shimao Quarry Hotel in the city's southwest is being built in an abandoned open-cast mine the size of five football fields. Total cost will exceed 1 billion yuan (S$204 million) once its interior has been fitted out.
With 16 of its 18 floors underground, it has been called a wonder of modern engineering.
Chief engineer Chen Xiaxiang said while normal projects use tried and tested technology to transport materials upward, this undertaking has required novel solutions to achieve the opposite.
"It's been a fight against gravity," he said.
The "fight" has mustered more than 5,000 architects, engineers, designers and workers, from initial design in 2006 to interior decoration today.
Along the way, Chen's team has registered 39 patents and made hundreds of technological breakthroughs.
One innovation, for example, solved the problem of pumping concrete downward by 77 meters without blockages, or separation of sand and cement, by changing the ratio of constituent materials and adding a damping device.
"Many of the problems we encountered were unprecedented," Chen said. "We had no technologies to import or copy."
The hotel is the design of Atkins, the engineering and architectural consultancy behind the Burj Al Arab hotel in Dubai, although Chinese teams have made it a reality.
When complete it will have 336 rooms and suites, an underwater restaurant, and all the amenities of a five-star hotel.
Shanghai Shimao Group has invested and developed the structure, while hospitality group InterContinental will manage the completed property.
A cartoon-themed park will feature on the floor of the quarry.
The unique layout will allow patrons to engage in extreme sports, including rock climbing and cable sliding.
According to Shanghai Shimao, company founder and chairman Xu Rongmao discovered the quarry while touring his real estate projects in the area, and envisages a world wonder to compete with the likes of the Dubai hotel.
Once operational, the bottom room will be about 600 meters lower than the presidential suite of the J Hotel on the 109th floor of world's second-tallest building, Shanghai Tower.
Both hotels have delayed opening for years.