It has been known as a settlement since the 15th century. 4-5 km from the city there are the remains of the medieval city of Agsu or Yeni Shamakhi, called "Ruined City". It got its name from the river of the same name in the area.
Abbasgulu Agha Bakikhanov mentions in his work "Gulustani-Iram" that in May 1735, Nadir Shah founded a new city in the 4 trees (37 km) of Shamakhi city, in a very favorable location called Agsu. This is related to the relocation of the Shamakhi population to Agsu during that period. The remains of the ancient city, a relic of the 17th century (currently called "Ruined City") are located in the south of the modern city of Agsu.
In the 18th century, the medieval city of Agsu became the largest city in Azerbaijan in terms of population and territory. The fortress built by Nadir Shah near Agsu village in May 1735 was the most important residence in this region for a long time.
Although the city was built in a short time, the most sophisticated urban planning of its time was applied. Stone-paved streets and roads, water and sewage lines, craft workshops, etc. were discovered during the excavations. it indicates a modern progressive urban culture for its time.
Some interesting objects for tourists are the "Agh Gunbez" mausoleum in the southwest of the city, the ruins of buildings from the 18th century in the east of Agsu, and the Maiden's Castle in Gurjuvan village.
On October 22, 2019, by order of the President of the Republic of Azerbaijan, Ilham Aliyev, the "Medieval Agsu City" State Historical-Cultural Reserve was established on the basis of the "Medieval Agsu City" Archaeological Tourism Complex.