The Alpine settlement Lahij located in Ismayilli region of Azerbaijan is an original monument of antique urban and architectural art. This medieval town with cobbled streets and squares is one of the most famous craft and trading centers in the Caucasus and beyond. It is believed that the legendary Manomakh’s cap, worn by Russian tsars for many centuries, was made here. Lahij became especially famous for manufacturing knives and copper utensils, decorated with engraved designs. Even today a dozen workshops operate here, demonstrating hereditary blacksmiths who make various household items in front of the astonished tourists. The very first residential block in Lahij was founded in III-IV centuries. It is astonishing that the water supply and sewage system, operating in the city, is about one and half thousand years old! The two km long tri-level sewer is paved under the main street, to a depth of 1 m. The upper two levels of the pipes are for the drinking water and water for industrial purposes. The lower part of the sewer is a rectangular trough lined with river stone. It is designed for wastes that come through the holes provided in the yard of every home. None of the residents know where the drainage begins and where it ends, and the principle of how it works, yet the collector has been functioning for many centuries. Now Lahij is a historical and architectural memorial protected by the state and the appearance of the settlement is preserved in its original form.