Temple of heaven - North gate

There is a door for each cardinal point. The emperor used the west gate when he went in procession to the temple where he was required to attend at least three ceremonies a year :

- The one of the winter solstice to account for its management in heaven. The ceremony lasted 4 days and the emperor dwelled in the hall of abstinence.

- The one of the first moon of the year (in February) to pay homage to Heaven in order to have his mandate renewed.

- The one of the summer solstice to sacrifice to Heaven for good harvests.

The temple of Heaven was built in the 15th century (ditto the Forbidden City) under the Ming dynasty to worship Heaven (with a ceremony of offering and sacrifices of animals) for the reign of the emperor as well as for good harvests.
It was originally called the temple of Heaven and Earth (there are symbols for both of them...) before being referred as only temple of Heaven in the 16th century. Under the Qing, emperor Qianlong enlarged it again in the 18th century...
The ceremonies ended in 1912 with the fall of the Empire and the birth of the Republic.