The crowning glory of the Temple of Heaven is the Hall of Prayer for Good Harvests, its triple-eaved roof canopy of glazed blue tiles reflecting its heavenly, as opposed to royal (yellow), status. The hall is entirely made of wood without the use of nails, the heavy roof supported by 28 wood pillars.
First built around 1420, it was burnt to cinders in 1889 and heads rolled in apportioning blame (although lightning was the most likely cause). A faithful reproduction based on Ming architectural methods was erected the following year; with timber imported from the USA since China by that point lacked trees big enough for the task.
Rich in esoteric symbolism, the four largest central pillars represent the seasons, the 12 in the next ring the months of the year, and the 12 outermost columns represent the day, broken into 12 ‘watches’ of two hours each. Writhing on the ceiling is a vivid dragon-phoenix relief, representing the emperor and empress.