Sage Agastya asked Lord Kartikeya how the sacrosanct place, Kashi came into being. He also asked how Kashi became famous as a place capable of giving salvation to a man.
Lord Kartikeya revealed to Agastya that once Parvati had asked Lord Shiva the same question. Lord Shiva had told her--' At the time of deluge when every thing had submerged in the ocean and darkness prevailed everywhere, only BRAHM-the embodiment of truth existed at that time and nothing else. BRAHM, the absolute truth is indescribable and inexpressible. No name can be attributed to HIM. HE is the absolute truth, the ultimate knowledge, the infinite, the omnipresent and the eternal bliss. Though basically formless HE attained a form on account of HIS own wish. That form is none other than me. Later on I created Prakriti from my body. All three of us (Shiva, Parvati and Kashi) manifested simultaneously by the grace of 'Aadi purush' (The Almighty God).'
Continuing with the tale of Kashi's greatness, Kartikeya told Agastya-' There is no holy place as dear to Lord Shiva as Kashi, which is not abandoned by him as well as his consort-Parvati even at the time of deluge. Lord Shiva named this holy place- Ananda van, because it gave immense joy to him. Subsequently, Lord Shiva and goddess Jagdamba put a glance on the left portion of their respective bodies as the result of which a divine entity manifested himself who was none other than Lord Vishnu and who was named Purushottam by Lord Shiva. Lord Shiva after blessing Purushottam went away. Later on, Lord Vishnu created a divine reservoir with his sudarshan chakra and filled it up with his sweat. He then engaged himself in an austere penance. Lord Shiva once again appeared along with Parvati and blessed Vishnu by saying-' This holy place will become famously known as Manikarnika because this is the very place where I had once lost my diamond ear-ring.'
Lord Vishnu made a request to Shiva --' May this place fulfill the wishes of those who seek salvation. Since it is blessed with your eternal presence hence its another name would be Kashi.'
Lord Shiva assured Vishnu by saying- ' This sacrosanct place is very dear to me and no event takes place here against my wish. Even if a person living here happens to be a sinner he has nothing to fear because I protect him. One who lives far from Kashi but remembers it with reverence becomes absolved of all his sins.'
There is a magnificent Shiva-linga at Kashi famously known as Kashi Vishwanath. Here is situated one of the twelve Jyotirlingas. Just as the Sun is visible in the whole world despite its presence at a particular point in the horizon, in the same manner Kashi has its influence throughout the length and breadth of the world.