Actors Tom Cruise, John Travolta and Kelly Preston were among scores of Scientologists gathered to celebrate the dedication of a palacial $145 million (NZD$174 million) 'cathedral' in Clearwater, Florida.
While church leaders told the city to expect around 10,000 Scientologists at the grand opening, a crowd of less than 6,000 people turned out, the Tampa Bay Times reported.
The enormous 377,000-square-foot Flag Building is the tallest building in downtown Clearwater, and has been in construction for nearly 15 years.
Church leader David Miscavige hosted the dedication ceremony that lasted just eight minutes and ended with a burst of silver confetti.
Clearwater locals were forced to watch the festivities from behind 6-foot-tall privacy fences and trees. Anyone who attempted to get close was stopped by church security staffers.
The notoriously secretive Church of Scientology has revealed little about what is inside the impressive palm-fringed colonial-inspired building. However, building plans submitted to the local council show a basement dining facility, offices, course rooms and hundreds of small rooms for Scientology's core counselling practice called "auditing".
The sixth floor contains a large circular track. Scientologists allegedly run until they achieve what founder Ron Hubbard called a "cognition," or moment of enlightenment.
The building was constructed for Scientologists to be able to participate in what is described as the "Super Power program".
The Super Power program was developed by Ron Hubbard and described as one of his greatest discoveries, the Daily Mail reports.
"Super Power is a series of spiritual counselling processes designed to give a person back his own viewpoint, increase his perception, exercise his power of choice, and greatly enhance other spiritual abilities," church spokesman Ben Shaw said in a statement.