Sisupalgarh is a ruined fortification at the outskirt of Bhubaneswar, capital city of state of Odisha (earlier known as Orissa) in the eastern part of Peninsular India. It is said to be one of the largest and best preserved early historic fortification in India. It is on the way to Puri.

Sisupalgarh is a nationally protected monument. It is claimed that the city to be at least 2,500 years old. It is believed to be existence of a flourishing urban life during the pre-historic period here in Sisupalgarh. Sisupalgarh was absolutely visible through naked eyes as well as from the space and this could be one of its kinds of cultural heritage in the whole of eastern India, the researchers claimed. It seemed to be a large city, which could have been governed under one ruler. On the basis of the architectural pattern and artefacts discovered during the early excavations, B.B. Lal, a renowned Indian archaeologist, concluded that this fort city flourished between 3rd century BC and 4th century AD. On the basis of the new findings, M. Smith and R. Mohanty claim that the fortified city flourished from around 5th century BC and probably lasted well after the 4th century. Thus, it is believed that this defensive settlement originated prior to the Mauryan empire.

M. Smith and R. Mohanty during their research found house foundations of laterite block architecture. The habitation areas also contained very large quantities of household pottery such as bowls and jars along with other household artefacts such as iron nails and terracotta ornaments including bangles, finger rings, pendants and ear spools.

Pointing out that the latest debris deposits and pillars indicated that it was meant for public use, Ms. Smith said the ancient artisans at Sisupalgarh were manufacturing potteries massively and those were in rapid use.

"It suggested that the people, animals and trash were closely integrated in the crowded space of the city. Moreover, they might have practised the same wasteful consumption which is witnessed in the modern day cities," said Ms. Smith, an anthropologist.

The population of the city was estimated to be around 20,000 to 25,000. Sisupalgarh is larger in surface than Jaugada, a contemporary fort situated at a distance of 10 kms from Purushotampur in Ganjam district of Odisah state. Sisupalgarh's defences were the highest known at that period in India. The gates themselves measure over 90m in length from the inside to outside and vary considerably in size, shape and in details of building.