Patliputra was started by Ajatsatru as a fort on the junction of 4 rivers, particularly the Ganga and Sone. This was to defend the kingdom of Magadh from the army of the Licchavis that used to cross the river Ganga and harass the citizens on the other side of the river. Legend has it that it was named after a princess gave birth to a baby son (Putra in Hindi). But in historical terms it was built as a fort by King Ajatsatru to prevent the Licchavis soldiers from attacking and harassing the people of Patliputra. In its early days it was built as a fort for the Magadh soldiers to rest. When a Magadhan soldier planted some roses near the camp it came to be known as "Kusumpur" (rose is kusum in Hindi). More on Legend of Patna.
The history and tradition of Patna go back to the earliest dawn of civilization. The original name of Patna was Pataliputra or Patalipattan and its history makes a start from the century 600 B.C. Patna covers area of 42 sq km. The name Patna has undergone many changes at its earliest stages like Pataligram, Kusumpur, Patliputra, Azimabad, etc., ultimately terminating to the present one. Chandragupta Maurya made it his capital in the 4th century A.D.
Patna city has been identified with Pataliputra (the Palibothra of Megasthenes, who came as ambassador from Seleucus Nicator to Chandragupta about 300 B.e.). Megasthenes describes Palibothra as being the capital of India. He adds that its length was 80 stadia, and breadth 15; that it was surrounded by a ditch 30 cubits deep, and that the walls were adorned with 57 o towers and 64 gates. More on ancient Patna.
The archaeological remains of ancient Pataliputra namely the Eighty pillared hall and Arogya Vihar are located at Kumrahar about six kms east of Patna railway station.
Ancient literature refers Pataliputra by various names like Pataligrama, Patalipura, Kusumapura, Pushpapura or Kusumdhvaj. In 6th Century B.C. it was a small village where Buddha, sometime before his mahaparinirvana, had noticed a fort being constructed under the orders of King Ajatasatru of Rajagrih for defence of Magadh kingdom against the Lichchavi republic of Vaisali. Impressed by its strategic location king Udayin, son and successor of Ajatasatru, shifted the capital of Magadh from Rajgrih to Pataliputra in the middle of 5th Century B.C. For about next thousand years Pataliputra remained the capital of great Indian empires of Saisunaga, Nanda, Maurya, Sunga and Gupta dynasties. The place has also been an important centre of activity in the fields of education, commerce, art and religion. During Asoka's time the third Buddhist council was held here. Likewise Sthulabhadra, the eminent Jain ascetic had convened a council here during the time of Chandragupta Maurya.
The first vivid account of Pataliputra including its municipal administration comes at about 300 B.C. from Megasthenese, the celebrated Greek ambassador at the court of Chandragupta Maurya, who mentions it as Palibothra in his book named Indica. According to his account the spread of the city was like a parallelogram, about 14 kms east-west along the river Ganges and 3 kms north-south. The circumference of the city was about 36 kms. The city was protected by massive timber palisades and further defended by a broad and deep moat which also served as a sewer of the city. Kautilya also in his book Arthasastra indicates wide rampart around the city. Remnants of the wooden palisades have been discovered during a series of excavations at Lohanipur, Bahadurpur, Sandalpur, Bulandibagh, Kumrahar and some other locations in Patna.
The Mauryan pillared hall at Kumrahar was brought to light by excavations conducted by Archaeological Survey of India in the years 1912-15 under D.B. Spooner with the funds donated by Sir Ratan Tata. In this excavation traces of 72 pillars were found. Further excavations in 1951-55 by K.P. Jayaswal research Institute, Patna exposed 8 more pillars of the hall and four additional ones belonging to the entrance or porch. Since then it is popularly refered as the 'Eighty Pillared Hall'.
All the pillars were made of black spotted buff sandstone monoliths with a lustrous shine typical of the Mauryan period. Regarding the nature of this hall, it has been variously assigned as the palace of Asoka, audience hall, throne room of Mauryas, a pleasure hall or the conference hall for the third Buddhist council held at Pataliputra in 3rd Century B.C. during the reign of Asoka.
Excavations by K.P. Jayaswal research Institute have unearthed brick structures of Gupta period identified as Arogya Vihara or hospital-cum-monastery on the basis of an inscribed terracotta sealing discovered from the place which bears the inscription reading 'Sri Arogya Vihare Bhikshusanghasya'. Another small red potsherd was also found inscribed with the word 'Dhanvantareh', possibly referring to the name or the title of the presiding physician of Arogya Vihar. Hence it can be surmised that this hospital was run by Dhanvantari, the famous physician of Gupta period.
Important finds from the excavation of this area include copper coins, ornaments, antimony rods, beads of terracotta and stone, dices of terracotta and ivory, terracotta seals and sealings, toy carts, skin rubbers, terracotta figurines of human, bird and animals and some earthen utensils. An exhibition hall at the site depicts the story of Kumrahar through antiquities, photographs, translites, diorama and other illustrations for the convenience of visitors.