The Golden Buddha (officially it seems to be named Golden Buddha Sukhothai Traimit) is housed in a small building in the rather nondescript, but old Wat Traimit. It is about 3 meters in height and weights an astonishing 5 tons (of gold).
Its history is not yet fully clarified. It may have been built during the late Sukhothai period or the Ayutthaya period. The - then still covered with plaster - Buddha image was moved to Bangkok (as many other Buddha Statues) during the third reign of the Rattanokosin era. It actually must mean (even though the Golden Buddha inside was unknown at the time) that this Buddha image had importance.