Koṭaratīrtha is a tīrtha on the bank of the Śābhramatī. Bhagavān Kṛshṇa installed the image of the devī Koṭarākshī here, after he freed Aniruddha from the city of Bāṇāsura. The place is also called Siddhakshetra.

Origin

Aniruddha, the grandson of Bhagavān Kṛshṇa, was chosen by Citralekhā for Ūshā and taken to the city of Bāṇāsura. Bāṇāsura held him captive with nooses and arrows. Aniruddha remembered Koṭarākshī, the divine power of Bhagavān Vishṇu that protects, and she answered his hymn of remembrance and came to his help.

Then came the great battle in which Bhagavān Kṛshṇa defeated Bāṇāsura. He returned to Dvārakā with Aniruddha. After that he installed Koṭarākshī on the bank of the Śābhramatī, and this made the tīrtha. The Padma Mahā Purāṇa tells this in the Uttara Khaṇḍa, Chapter 159.

Devī Koṭarākshī

The Purāṇa describes Koṭarākshī in many forms.

She is the śakti (power) of Bhagavān Vishṇu, always busy protecting devotees.
She has all forms, great divine power and superior strength.
She is named as Tripurā, the destroyer of Tripura, as Śiva, and as the form of Śiva.
She is named as the daughter of Sarasvatī, and as Durgā, Bhairavī, Bhairavākshī and Lakshmī.

The men who recite the hymn that Aniruddha composed in her honour are freed from bondage.

Merit of bathing here

A man who bathes with care at this tīrtha for one year, and sees the face of Koṭarākshī, gains great wealth. A man who bathes at Siddhakshetra and sees the devī at Koṭara is honoured in Rudra’s svarga (heaven). Even to remember her gives moksha.

Sources

Padma Mahā Purāṇa, Uttara Khaṇḍa, Chapter 159