There is no such thing as an antigravity room, because it is impossible to completely eliminate gravity. However, NASA has several means of creating a microgravity, or extremely low gravity environment, including drop towers, a special aircraft flying in parabolic arcs and water tanks in which people are given weights to make them neutrally buoyant.
To simulate microgravity, Johnson Space Center at NASA uses the C-9 Low-G flight research plane known as the "Vomit Comet." An earlier version, the KC-135, was used by the film crew of the movie "Apollo 13" to shoot zero gravity scenes. NASA's Zero Gravity Research Facility uses two drop towers which simulate near-weightless environments, one for 5.18 seconds and the other for 2.2 seconds. In the larger 467-foot tower, hardware equipment is dropped in freefall in a vacuum chamber for a distance of 432 feet. NASA's water tanks are not true microgravity facilities, but astronauts preparing for spacewalks train in the neutrally buoyant environment.
Though true antigravity is an enticing proposition, it may prove to be impossible. Even space is not devoid of gravity. At typical orbital altitudes, gravity is still quite strong, and it is gravity that keeps the space station and satellites orbiting around the Earth. Gravity is even the force that keeps planetary bodies revolving around each other.