Tehran, Iran (CHN) - Iranian and British archeologists have unearthed the ruins of a Sassanid city in the course of excavations at the Great Wall of Gorgan.

The Sassanid city is located two kilometers to the north of the wall and spans an area of approximately 50 hectares.

"The team has found coal, earthenware and animal skeletal remains, which suggest the city was built over an Iron Age settlement," said team director, Hamid Omrani.

"Geophysical studies show that the Sassanid city was surrounded by a trench and had inter-connected streets and a citadel in the center," he added.

Experts say that houses were built from bricks dating back to the late Sassanid and early Islamic eras and were different from those used in the Gorgan Wall.

Previous excavations yielded a fortress and an ancient canal, which was used to direct water from the Gorgan River to the fortress.

The Great Wall of Gorgan, also known as the Red Snake, is located in Iran's northern Golestan Province and includes water channels, an aqueduct, and over 30 military forts which were once densely occupied with military style barrack blocks.

The wall was built during the Sassanid era more than 1,000 years before the construction of the Great Wall of China.