ITS windows are blacked out, cameras monitor every entrance and security guards are on 24-hour patrol.
Inside the imposing, hotel-sized building workmen put the finishing touches to a series of rooms packed with space-age equipment aimed at boosting the "superpower" of its users.
It may sound like something from Tom Cruise's next film Mission: Impossible 4, but this is the latest venture of the Church of Scientology, which has the Hollywood superstar as its most famous devotee.
Cruise is expected to attend the grand opening of what is known as The Super Power Building, which has nearly 900 rooms and has taken more than 13 years to build at a cost of £50million.
Fellow film stars John Travolta and Kirstie Alley are also expected to be there.
The building in Clearwater, Florida, has been shrouded in secrecy since its foundations were first laid.
And when The Sun tried to find out about the imposing structure, it turned out to be Mission: Impossible.
Within minutes of arriving outside the entrance a security guard stepped out from behind a blacked-out door to monitor us.
Moments later another guard on a mountain bike peddled up and asked what we were doing. He wore a white shirt and black trousers, the uniform adopted by many Scientology staff.
Later, yet another security guard began filming us before ducking behind a tree when we trained our camera on him.
Attempts to find out what will happen in the Super Power Building were met with silence by officials.
The veil of secrecy does not surprise experts who have followed the religion since it was founded by the late science fiction writer L Ron Hubbard in 1952.
Someone who has spoken to dozens of former members, said: "Scientology claims not to be a cult but all they do gives that impression. They don't like people snooping around what they are doing."
A series of alleged artists' impressions of the interior that were leaked on to the net have revealed NASA-like training gizmos that will be used to help devotees of the religion to boost their so-called "theta powers".
The building houses an ANTI-GRAVITY SIMULATOR central to boosting devotees' mental abilities. Users are strapped blindfolded into the machine which spins around and is said to aid perception of direction.
Other rooms contain a VIDEO SCREEN that moves back and forwards while flashing up images. It is said to help users enhance their ability to spot subliminal messages.
The centrepiece of the 12-storey building is the sixth-floor INDOOR RUNNING TRACK the length of the structure, which is kept in semi-darkness.
An insider said Scientology worshippers will be encouraged to run until they are close to exhaustion and their mind freed of painful memories.
The highly secret Super Power course was developed by Hubbard and is said to boost a person's perceptions or senses through mental and physical exercises. Scientologists believe that in addition to the five senses of hearing, sight, touch, taste and smell, we all have 57 extra "abilities".
These include being able to sense blood circulation, balance and know compass direction, temperature and gravity as well as have an "awareness of importance, unimportance".
Almost half the building's 889 rooms will be used to carry out "audits" — the Scientology term for counselling sessions.
Auditing is a cornerstone of the religion, which all members must undergo. It is said that a museum dedicated to Hubbard will be on the ground floor, plus murals depicting famous moments in Scientology's history.
The Super Power Building is connected by a walkway to a luxury hotel, Fort Harrison, used as a retreat exclusively by Scientology members. The hotel is also ringed by CCTV cameras and security guards hover at the entrance.
Both Pulp Fiction star Travolta and Alley, best known for TV's Cheers, are regular visitors. Tom Cruise has also spent time at Fort Harrison. The Top Gun star is by far the most high-profile of the estimated eight million who follow the Church of Scientology worldwide.
Cruise has helped raise hundreds of thousands towards it. He joined the religion in the late Eighties.
Other celeb followers include actor Will Smith, Elvis Presley's daughter Lisa Marie, actress Juliette Lewis and My Name Is Earl star Jason Lee. Cruise rarely talks in public about his devotion but he has appeared at many official functions.
Insiders say he is second in command to Scientology leader David Miscavige in all but name.
The Super Power Building's £50million costs were met by followers, but Cruise's name does not appear on a list of donors leaked by ex-members.
Kirstie Alley is reported to have donated more than £160,000. Scientology's main headquarters in Britain is in Saint Hill, West Sussex, but quiet Gulf Coast town Clearwater — a popular spot for Brits after they have visited Orlando's Disney World — has become ground zero for the religion.
The building is expected to draw many more Scientologists to the area. Over the past two decades the church has become the largest single property owner in Clearwater.
Many residents resent the takeover but are afraid to speak out. "They have such an imposing presence that no one wants to say anything against them," said one local. "You hear so many stories about harassment of people who dare to speak out against them."
Nancy Beckman, 78, who runs a Christian Science Reading room close to the Super Power Building, said: "I call them the ants. All you see are lots of people wearing black and white scurrying around. I have nothing against them but they are secretive. A lot of people do not feel secure around them."
She said visitors to Clearwater were "mesmerised" by the Super Power Building.
"Clearwater is the training ground for Scientology and they are here to stay," she said.
Another resident, who would not be named, said Scientology is nothing more than a cult.
"Most people follow the teachings of religious scripts, Scientologists follow those of a failed science fiction writer," they said.
"That tells you all you need to know about their church."