The Temple of Heaven is located in southern Beijing．It was first constructed in 1420, the 18th year of the reign of Ming emperor Yongle，and was extended and renovated during the reigns of Ming emperor Jiajing and Qing emperor Qianlong．It was the place where the emperors of the Ming and Qing dynasties would worship the god of heaven and pray for good harvest. It is also quite big and covering an area of 273 hectares. It is the largest architectural complex in the world for rituals to pay homage to heaven… In Beijing this is the most important of the four temples.

Access to the parc is easy, and the east entrance is just a few steps away from the metro station (Tiantandongmen on line 5). There are actually two sections and thereby different entry tickets. One is entry to the parc grounds and the other entry to the temples. Parc is quite big and nice. A lot of pensioners go there daily, especially to play cards in the long corridor. Of course, the main attraction for the tourist is the temple – the Hall of prayer for a good harvest, built in 1420, the 18th year of the reign of Emperor Yongle of the Ming Dynasty (1368 – 1644). It was destroyed in 1889 by a thunderbolt and rebuild a few years later. The internal structure of the hall is unique, using 28 massive wooden pillars and 36 square rafters, interlocked without nails to support the entire structure. There is no steel and cement used. The four dragon pillars in the center are 19 meters high and 1.2 meters in diameter, representing the four seasons. The twelve gold pillars in the middle circle represent the 12 months of the year, and the 12 pillars in the outer circle represent the 12 divisions of day and night.

Further south is a Danbi bridge, which connects the Hall of prayer for a good harvest with Imperial Vault of Heaven and Circular Mound Altar. Imperial Vault of Heaven is surrounded by the Echo wall. The wall is flat and smooth, which allows sound waves passing smoothly. However, due to the number of “loud” visitor it is almost impossible to experience the mysterious atmosphere here.

Source: http://www.travelchinaguide.com/attraction/beijing/temple-of-heaven/