The Ancient library database in Atlantis can be accessed from any of the workstations around the city, however the holo room also provides the option to interact directly with a holographic interface when conducting a search of the database. Used sparingly by the Atlantis expedition because of its heavy power drain, the holo room program was originally designed by the Ancients to teach very young children the Lantian systems. The room contains a central platform supporting a single pedestal with a console. Stepping onto the platform activates the device, and the holographic image of a person appears which can act as the communication interface. It is possible to enter a question manually on the console or to speak the question orally, and the hologram responds to the questions by providing the information that is requested.
When Daniel visited Atlantis, he used the holo room to search for information that would lead to the discovery of Merlin's weapon to defeat the Ori. He became suspicious, however, when the holographic image of a woman not only provided him with information that should not have been part of the Ancient database, but also addressed him directly by name. It became clear that the image was not a hologram at all, but was instead Morgan Le Fay, an ascended Ancient who was posing as a holographic image in the hope of guiding Daniel's quest through technology without violating the Ancient laws against noninterference.
Cross Reference: Atlantis, Holographic Projection, Morgan Le Fay
Episode Reference: The Pegasus Project