Mbh 3.87.1b

And, O bull among the Bharatas, there also, in that place, is the Kausiki, whose basin abounds in various fruit and roots, and where Viswamitra endued with wealth of asceticism acquired Brahmanahood. Towards that direction also is the sacred Ganga, on whose banks Bhagiratha celebrated many sacrifices with profuse gifts (to Brahmanas). They say that in the country of Panchala, there is a wood called Utpala, where Viswamitra of Kusika’s race had performed sacrifices with his son, and where beholding the relics of Viswamitra’s superhuman power, Rama, the son of Jamadagni, recited the praises of his ancestry. At Kamyaka, Kusika’s son had quaffed the Soma juice with Indra. Then abandoning the Kshatriya order, he began to say, I am a Brahmana.’ In that quarter, O hero is the sacred confluence of Ganga and Yamuna which is celebrated over the world. Holy and sin-destroying, that tirtha is much regarded by the Rishis. It is there that the soul of all things, the Grandsire, had, in olden days, performed his sacrifice, and it is for this, O chief of the Bharata race, that the place hath come to be called Prayaga. In this direction, O foremost of kings, lieth the excellent asylum of Agastya, O monarch, and the forest called Tapasa, decked by many ascetics. And there also is the great tirtha called Hiranyavinda on the Kalanjara hills, and that best of mountains called Agastya, which is beautiful, sacred and auspicious. In that quarter, O descendant of the Kuru race, is the mountain called Mahendra, sacred to the illustrious Rama of the Bhrigu race. There, O son of Kunti, the Grandsire performed sacrifices of yore. There, O Yudhishthira, the sacred Bhagiratha entereth a lake and there also, O king, is that sacred river known by the name of the merit-bestowing Brahmasara, whose banks are inhabited by persons whose sins have been washed away, and whose sight alone produceth merit.