The square altar (symbolizing earth) measures 54 meters on each side, featuring yellow stone balustrades and two stone dragons guarding the main entrance.

The Kinh Thien Altar is situated on An Son peak, in Binh Phu commune (formerly Tay Son district, Binh Dinh province). An Son is a low mountain on the right bank of the Kon River, surrounded by the Hoanh Son mountain range. The complex, completed in 2012 and spanning over 28 hectares, earned provincial-level historical relic status in 2017. It comprises three main areas: the Kinh Thien Altar, the An Temple - Thong Linh Tower, and administrative buildings. All structures are symmetrically arranged along a north-south sacred axis.

The altar for heaven and earth occupies the highest position, reflecting the "three powers" philosophy: heaven, earth, and humanity. The main altar, located on the uppermost level, is circular with a diameter of 27 meters, symbolizing heaven. It features 9 red stone steps divided into three tiers. At its peak stand 12 stone pillars, representing the 12 hours of the day, each carved with a unicorn. A stone incense table dedicated to heaven and earth sits at the center of the altar.

The Thong Linh Tower is square, with 7 stories symbolizing the connection between humanity and heaven, and between past and present.

Stone dragons and unicorns are placed at both the main altar and the square altar.

The lowest level of the heaven altar features 4 gates opening in 4 directions. The main south gate is Bao Son Thien An, the north gate is Binh Dinh Mon, Thien Ung Mon is located to the west, and Khai Duc Mon is positioned to the east. This square altar measures 90 meters on each side.

Stone horses and statues of civil and military mandarins stand on both sides of the An Temple entrance, representing the forces that contributed to the Tay Son cause.

Inside the temple are three chambers: the front chamber is dedicated to generals and righteous soldiers, the central pavilion houses a stone tablet inscribed with a replica of the "Son Ha Xa Tac" seal, and the rear sanctuary honors the three brothers Nguyen Nhac, Nguyen Hue, and Nguyen Lu.

According to the Quang Trung Museum, while But Son on the left bank of the Kon River was where Nguyen Nhac was enthroned as king by the Jade Emperor, it was on the right bank, at An Son, that he received the imperial seal inscribed with the 4 Han characters "son ha xa tac" (mandate of the nation).

Legend has it that during a death anniversary feast at Nguyen Nhac's home, the sounds of gongs and drums, along with flickering lights, echoed from Hon Trung peak in the night. Nguyen Nhac ascended the mountain and was presented with an imperial edict by a celestial elder, proclaiming, "The Jade Emperor decrees Nguyen Nhac as king"". From then on, this rumor spread widely, solidifying Nguyen Nhac's authority as one chosen by heaven.

The path leading to the heaven altar.

Nguyen Van Tan, Deputy Director of the Quang Trung Museum, stated that the altar for heaven and earth holds significant meaning in praying for national prosperity, peace, and stability. Annually, approximately 28,000 to 30,000 visitors come to explore and admire the site.

Tran Hoa