The Circular Mound

　　Built in the ninth year of the Jiajing reign (1530), it faces south with red palace walls all around, topped with green glazed tiles, commonly known as the “child wall”. Each side of the child wall has a main gate. The northern gate is called Chengzhen Gate, also known as the North Heavenly Gate; the eastern gate is called Taiyuan Gate, also known as the East Heavenly Gate; the western gate is called Guangli Gate, also known as the West Heavenly Gate. The main southern gate is called Zhaoting Gate, also known as the South Heavenly Gate. Each gate bears an inscription combining Manchu and Chinese characters. Arranged in sequence, the second characters of the gate names form the words Yuan (元), Xiang (享), Li (利), and Zhen (贞). “Yuan” represents the birth of all things, with heaven and earth creating without bias; “Xiang” signifies the flourishing and smooth growth of all things; “Li” stands for the harmony of yin and yang between heaven and earth, enabling all things to grow appropriately; “Zhen” means the unchanging harmony of yin and yang, ensuring that all things can remain stable and enduring.

　　Outside, there are two layers of circular walls, with a three-tiered circular stone altar in the center. The upper tier is surrounded by edge stones, and at the center lies a round stone slab called the “Heaven’s Heart Stone.” Around it are nine stone slabs, followed by 18 in the next circle, increasing by nine stones per layer until reaching 81 stones in the “nine times nine” layer, symbolizing the “Nine Heavens.” When standing on the Heaven’s Heart Stone and speaking, your voice sounds particularly deep and loud.

　　The artistic features of the Temple of Heaven architecture are mainly reflected in the ingenious use and thoughtful design of acoustic, mechanical, and aesthetic principles: First is the “Heaven’s Heart Stone,” where all seem to follow. When you stand on the central heart stone of the upper tier of the Circular Mound and speak, you’ll hear pleasant echoes from all directions, as if awakening a sense of mystery in one's consciousness and immersing the whole soul in an auditory illusion.

　　This is because the position of the heart stone is precisely at the center of the Circular Mound. The stone altar is surrounded by three tiers of stone railings, and outside the stone altar are two layers of reverse walls. When sound emitted from the heart stone hits the surrounding stone railings and reverse walls and is then refracted back toward the center simultaneously, the time it takes for the sound to travel from the radius of the Circular Mound and back is only 0.07 seconds. The speaker can hardly distinguish the original sound from the echo, and because the echo comes from all directions, the sound wave vibration is strong, making the sound not only loud and pleasant but also continuous.

　　The Circular Mound is located in the southern part of the Temple of Heaven and was the venue where emperors held the Winter Solstice Heaven Worship Ceremony, also known as the Heaven Worship Altar.

　　The main structures of the Circular Mound include the Circular Mound itself, the Imperial Vault of Heaven along with its auxiliary halls, the Divine Kitchen, the Three Stores, and the Slaughtering Pavilion. Supporting structures include the Dressing Platform and the Beacon Tower. During the Ming Dynasty, the Circular Mound was a three-tiered blue-glazed circular altar. In the fourteenth year of the Qianlong reign (1749 AD), it was expanded, and the blue glaze was replaced with bluestone slabs and white marble columns and railings.

　　When the emperor went to worship heaven each year, he would alight from his sedan chair under the western memorial archway, then walk through Zhaoting Gate and proceed to the Circular Mound. It is surrounded by two layers of low blue-glazed walls called “walls.” The first layer is square and called the outer wall; the second layer is round and called the inner wall, symbolizing “the round heaven and square earth.” At the center inside is the Heaven Worship Platform (also called the Prayer Platform), which is the Circular Mound platform.

　　The artistic features of the Temple of Heaven architecture are mainly reflected in the ingenious use and thoughtful design of acoustic, mechanical, and aesthetic principles: First is the “Heaven’s Heart Stone,” where all seem to follow. When you stand on the central heart stone of the upper tier of the Circular Mound and speak, you’ll hear pleasant echoes from all directions, as if awakening a sense of mystery in one's consciousness and immersing the whole soul in an auditory illusion.

　　The altar is an open-air three-tiered circle, symbolizing heaven. In ancient times, the odd numbers one, three, five, seven, and nine were called “yang numbers” or “heavenly numbers,” with nine being the ultimate yang number. Therefore, the number of tiers of the Circular Mound, the diameter of the platform, the number of paving stones, and the surrounding railings all use heavenly numbers to signify the supremacy and vastness of the heavens. The three-tiered round altar has a top tier platform diameter of nine zhang, called “one-nine”; the middle tier is fifteen zhang, called “three-five”; and the bottom tier is twenty-one zhang, called “three-seven.”

Temple of Heaven Park

Divine Music Administration

Hall of Imperial Zenith

Danbi Bridge

Hall of Prayer for Good Harvests

Imperial Vault of Heaven

Echo Wall of the Temple of Heaven