Kośala Tīrtha is a sacred site within Indraprastha. Bhagavān Vishṇu set it up there to stand for the two Kośalas: the northern one, where Bhagavān Rāma was born, and the southern one, Dakshiṇakośala, where Bhagavān Rāma killed Rāvaṇa.

Its waters have the power to free anyone who touches them, even without meaning to. The Padma Mahā Purāṇa shows this in the account of the brāhmaṇa Mukunda, whose bones a dog carried and dropped here. Mukunda was freed at once. His murderer Caṇḍaka also reached moksha (liberation) at this same tīrtha in the end.

Setting up within Indraprastha

Bhagavān Vishṇu made Indraprastha the sum of all sacred places. Within it he set up Dvārakā, Kośala, Madhuvana (Madhvāraṇya), Badarikāśrama, Haridvāra and Pushkara. So the Kośala Tīrtha within Indraprastha carries the full holiness of Bhagavān Rāma’s land.

The Purāṇa says there are two Kośalas. Uttarakośala is the northern Kośala, Ayodhyā, the city where Bhagavān Rāma was born. Dakshiṇakośala is the southern Kośala, where Bhagavān Rāma defeated Rāvaṇa. Both are present within the Indraprastha tīrtha. (Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapters 200 and 212)

Liberation of Mukunda

The brāhmaṇa Mukunda was murdered for his gold ornaments by his barber Caṇḍaka. After the cremation, a dog carried Mukunda’s bones. By good fortune it dropped them into the Kośala Tīrtha within Indraprastha.

At the moment the bones touched the holy waters, Mukunda was freed. A divine vehicle came for him, and he reached Vaikuṇṭha. This account shows that no deliberate pilgrimage is needed at this tīrtha. Touching its waters, even without intending to, is enough. (Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapter 211)

Liberation of Caṇḍaka

Caṇḍaka, the murderer, was reborn as a serpent because of the pāpa (sin) of killing his own patron (his guru or employer). He lived in that form for many ages near Indraprastha. In the end Caṇḍaka the serpent reached moksha at the Kośala Tīrtha, the same holy place that had freed his victim. The power of the tīrtha reached even the one who did the crime. (Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapter 211)

Bhagavān Vishṇu’s declaration

A brāhmaṇa was neglecting the Kośala Tīrtha. Bhagavān Vishṇu appeared to him in disguise and said himself that Indraprastha is the greatest of all holy places in the three worlds. He said:

All the holy places subsist within it.

Bhagavān Vishṇu also said clearly that both Dakshiṇakośala and Uttarakośala are present there. (Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapter 212)

Sources

Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapters 200, 209–212