Chidambara Ragasiyam/Rahasyam (Tamil for "secret of Chidambaram") is a Hindu belief that there is a secret message conveyed through the embossed figure near the shrine of Shiva in Chidambaram temple.
Since ancient times, it is believed that this is the place where Lord Shiva and Parvathi are present, but are invisible to the naked eyes of normal people. In the Chidambaram temple of Lord Nataraja, Chidambara Ragasiyam is hidden by a curtain (Maya). Darshan of Chidambara Ragasiyam is possible only when priests open the curtain (or Maya) for special poojas. People who are privileged to have a darshan of Chidambara Ragasiyam can merely see golden vilva leaves (Aegle Marmelos) signifying the presence of Lord Shiva and Parvathi in front of them. It is also believed that devout saints can see the Gods in their physical form, but no such cases have been officially reported.
The phrase "Chidambara Ragasiyam" really means something different. The pharse literally means a secret associated to Chidambaram - the place. Behind this is a real meaning to a secret. As described above there is a particular curtain kind of curtain which when removed enables us viewing the secret. The real significance of doing so is that, when the curtain which is "maya" is removed one can see his real self. And the seeing of oneself removing the curtain of maya is viewing the secret. According to legend, "Chidambara Ragasiyam" will never be revealed as it is the secret relating to a particular person who sees it removing the screen of "maya". In the temple, when the poojas are performed and the screen is removed, one will be able to see the secret only when he applies this to his mind and soul.