Construction of the Temple of Heaven was begun during the reign of Emperor Yongle, and completed in 1420. The temple complex was conceived as the prime meeting point of earth and heaven, and symbols of the two are integral to its design. Heaven was considered round, and the earth square; thus the round temples and altars stand on square bases, while the park has the shape of a semicircle beside a square. The intermediary between earth and heaven was, of course, the Son of Heaven – the emperor, in other words.
The temple was the site of the most important ceremony of the imperial court calendar, when the emperor prayed for the year’s harvests at the winter solstice. Purified by three days of fasting, he made his way to the park on the day before the solstice, accompanied by his court in all its magnificence. On arrival at Tiantan, the emperor would meditate in the Imperial Vault, ritually conversing with the gods on the details of government, before spending the night in the Hall of Prayer for Good Harvests. The following day he sacrificed animals before the Altar of Heaven. It was forbidden for commoners to catch a glimpse of the great annual procession to the temple, and they were obliged to bolt their windows and remain, in silence, indoors. Indeed, the Tiantan complex remained sacrosanct until it was thrown open to the people on the first Chinese National Day of the Republic, in October 1912.
The last person to perform the rites was General Yuan Shikai, the second president of the Republic, on December 23, 1914. He planned to declare himself emperor but died a broken man, his plans thwarted by opponents, in 1916.