Nam Giao altar stands amid tree ranges in Hue. Photo by VnExpress/Vo Thanh. 

Renovation of Hue's Nam Giao Esplanade, where Nguyen kings offered their annual prayers, has started and is expected to complete in 2023. 

Phan Van Tuan, deputy director of the Center for Conservation of Hue Monuments in Thua Thien-Hue Province, which manages Hue Imperial Citadel and other relics from the Nguyen Dynasty, said the total cost for the renovation project started on Thursday and is estimated at VND24 billion ($1.03 million).

Cracked sections along the walls will be reinforced while the gate systems are cleaned of moss to regain their original color. The foundation will be repaired and tiled too.

Built in 1806 under the reign of King Gia Long, Vietnam's first Nguyen Dynasty (1802-1945) emperor, the esplanade, also known as Nam Giao Altar, consists of three terraces symbolizing heaven, earth, and man. In the past, it used to be the place where Nguyen kings habitually offered animal sacrifices and elaborate gifts to deities each spring.

After more than two centuries, the monument has seriously deteriorated. It was inscribed as part of the UNESCO-recognized Hue Imperial Citadel by the government in 1993 and is thus under special protection.

Hue Imperial citadel is a leading tourist destination in Vietnam. It brought more than 4.8 million visitors to Hue in 2019, 2.1 million of them foreigners.