Phra Si Ratana Ched erected in 1855 by King Rama IV, the Main Stupa (mound-like or semi-hemispherical structure containing Buddhist relics, typically the ashes of Buddhist monks, used by Buddhists as a place of meditation) contains relics of the Buddha and is regarded as the most sacred of all stupa in the Royal Chapel.
In the hollow interior of the stupa is a smaller stupa containing the sacred relics