Before Rome was a city, there was Pataliputra. The Greek ambassador Megasthenes visited it in the 3rd century BCE and declared it the largest, most magnificent city on Earth. It was the capital of the Mauryan Empire — the first to unite the Indian subcontinent — governed by Ashoka the Great, whose Chakra sits at the centre of India's flag to this day.

Bihar is where the Buddha attained enlightenment. Where Mahavira founded Jainism. Where Chanakya wrote the world's first systematic treatise on economics and statecraft. Where Aryabhata calculated the value of pi and proposed that the Earth rotates on its axis — a thousand years before Europe caught up. Where Nalanda University educated 10,000 students from across Asia for seven centuries, until it was burned in 1193 CE and its library took three months to stop burning.

Ray takes you through the full sweep of Bihar's extraordinary history — from the Licchavi republic of Vaishali, one of the world's earliest democratic polities, through the Mauryan and Gupta golden ages, Sher Shah Suri who gave India the rupee and the Grand Trunk Road, to Gandhi's first Satyagraha in Champaran and JP Narayan's Total Revolution.

We meet Bismillah Khan, whose shehnai played at India's first Independence Day. We meet Ramdhari Singh Dinkar, whose poetry made Hindi roar. We meet Vidyapati, who gave Maithili its classical voice five centuries ago. And we eat litti chokha — the smoky, stuffed wheat ball that Sher Shah's army marched on, and that a homesick Bihari makes first whenever they miss home.

We stand at Bodh Gaya at dawn. We walk through the ruins of Nalanda. We wade into the Ganges at sunset for Chhath Puja — the most democratic festival in India, with no priest, no temple, just a devotee, the water, and the sun.

New episodes every Tuesday at 7pm. Next week — Chhattisgarh.

A river so wide you cannot see the other bank. Tea gardens stretching to the horizon. A one-horned rhinoceros moving through the morning mist. And a 600-year-old kingdom that repelled 17 Mughal invasions and never once surrendered.

This is Assam — the gateway to India's Northeast, threaded through by the mighty Brahmaputra, and home to some of the most extraordinary stories this country has to tell.

Ray takes you through the dramatic landscape of the Brahmaputra valley, the world's largest river island at Majuli, and the tea gardens that put Assam in a billion morning cups. We trace the history — from the ancient Kamakhya temple and the saint Sankardeva who built Assam's cultural soul, to the great Ahom kingdom and the Battle of Saraighat where Lachit Borphukan defeated the Mughals on the river.

We meet Bhupen Hazarika, whose voice was the sound of the Brahmaputra itself. We meet Hima Das — the Dhing Express — a farmer's daughter who became India's first world athletics gold medallist. We eat Masor Tenga and Khar and bamboo-shoot pork and til pitha made for Bihu. We visit Kaziranga, where the one-horned rhinoceros was pulled back from the edge of extinction in one of conservation's greatest victories.

And we dance Bihu. Because in Assam, that is how you say: this is who we are.

New episodes every Tuesday at 7pm. Next week — Bihar.

India's first light falls here. Before Mumbai wakes, before Delhi stirs, the sun touches the Himalayan peaks of Arunachal Pradesh — the Land of the Dawn-Lit Mountains — and India's day begins.

The largest state in the Northeast, Arunachal Pradesh stretches from the subtropical forests of the Brahmaputra plains to the permanent snowfields of the high Himalayas. It is home to over 26 major tribes and more than 100 sub-tribes, each with their own language, their own festivals, their own relationship with the land. Over 500 bird species. Four big cat species in a single national park. Sixty-plus tribal languages. And one of the great Buddhist monasteries of the world, perched at 3,000 metres above sea level.

Ray takes you through the dramatic geography, the peaceful integration of Tawang into India in 1951, and the living tribal cultures of the Adi, Apatani, Monpa, and Nyishi peoples. We eat bamboo-cooked rice and smoked pork and drink rice beer from a bamboo cup. We cross the Sela Pass at 4,176 metres. We stand in the courtyard of Tawang Monastery at dawn. We camp in a rice field in Ziro Valley as independent music plays under the stars.

This is India's frontier. Its most remote corner. Its first morning.

New episodes every Tuesday at 7pm. Next week — Assam.