The main building of the Temple of Heaven is the Hall of Prayer for Good Harvest and the emperors had held the ceremony of sacrificing to heaven there every year to pray for good weather and the bumper harvest. The Hall of Prayer for Good Harvest is a round hall with a pinnacle and triple eaves and was built based on the respect for God. The hall is nine zhang (about 27 meters) high and has a circumference of 30 zhang (about 90 meters), representing 30 days in a month. There are four pillars in the center of the hall, known as "Dragon-Well Pillars" which are about 19 meters high with the diameter of the larger end being 1.2 meters.