To know news of Kashi, Lord Shiva sent Yoginis, Surya Deva (Sun God) to Kashi. But they didn't return to Kailasha to deliver news. (It doesn't mean Lord Shiva didn't know news of Kashi, it is just his play. He always stays at Kashi as Vishwesa). Lord Shiva sent Brahma this time to know news of Kashi.
Lord Brahma went to Kashi on Swan and disguised as Brahmana went to King "Divodasa" of Kashi.
Chapter 52, Uttaraardha, Kashi Khanda of Skanda Purana mentions it in detail.
- The Self-born Lord with white Swan as his vehicle reached the city of Väränasi quickly and considered blessed, as one who has done his
duty.
- 'In this contact with Käsi, I have gained the benefit of having the Swan as a vehicle, since they say that there are obstacles in
regard to the attainment of Käsi at every step.
- The root drs' (to see) has become meaningful in regard to my Drsau (eyes) since this Ånandavätikä has come clearly within the range of my
vision.
Lord Brahma disguised Himself as Brahmana and told the king His desire to perform ten Ashwamedha Yajanas.
- Brahma, who was delighted in his mind after viewing the city of Väränasi, assumed the form of an aged Brähmana and visited the king.
- With raw rice-grains wet with water in his hand, he proclaimed Svasti unto the king. He was saluted by the king and offered a seat
which he occupied.
- The king duly honoured him by standing up and offering the seat and the like. On being asked the purpose of his visit, the Brähmana
said to the king:
He asked his desire to perform Yajna.
- May this chitchat be set apart. I shall state the thing relevant at present. O king, I am desirous of performing a sacrifice. Hence I
seek your help.
- O king, this kingdom has a benign king in you. It is the receptacle of all prosperities. I have some assets in the form of
great wealth accumulated by legitimate means.
- In this land of Karmas, the capital city is the most excellent one. Even on the day of annihilation, there is not reduction in the
power to yield benefits in the case of the holy rites.
- The wealth amassed by persons abiding by the righteous path, should be utilized in Käsi. Otherwise it will be conducive to pain
and distress.
King agreed to perform Yajnas and said he would provide all required materials.
54-57. The king said: O excellent Brähmana, whatever has been spoken
by you has been grasped by me in the heart. I am at your service in
the matter of helping you who are desirous of performing sacrifice.
Take away all the requisites for the sacrifice from my treasury.
Whatever I have in the kingdom consisting of seven constituent
elements, you are the lord unto that entirely. With singleinded
attention go ahead with the sacrifice. Consider that everything you
desire has already been accomplished. In my rule over the kingdom, O
Brähmapa, I have no selfish interest.
Brahma performed Yajnas there with king Divodasa and installed Brahmeswara Linga.
- Getting the help of the saintly King Divodäsa, the Lotus-born One performed in Käsi ten great horse-sacrifices.
- As the interspaces of the firmament were pervaded by the columns of smoke from the Homas, the firmament has not given up the bluish
colour ever since.
- Since that time onwards, that Tirtha has become wellknown all over the world. The Tirtha named Daéäévamedha in Väränasi is the bestower
of auspiciousness.
- Formerly that Tirtha was known by the name Rudrasaras. It later became 'Dasasvamedhika' due to its taking over by Brahmä.
- Thereafter, the heavenly river came into contact with it in association with Bhagiratha. Hence that excellent Tirtha became
extremely meritorious and sacred.
- After installing the Linga Dasäsvamedhesa there, Brahma stayed there itself. Even till today he has not left Käsi.
- He did not find any vulnerable point in that king who was extremely interested in pious acts. Hence what could Brahmä have said
after going to Lord Siva.
- He realized the power of the holy place. Meditating on Siva, the Lord of the universe, Brahmä installed Brahmesvara and remained there
itself.
Significance of Dashashwamedha Ghata:
Skanda said:
- O son of Mitra and Varuna, I shall narrate the greatness of Dasäsvamedha in Käsi, the crest-jewel of all holy spots.
- Whatever sacred rite, even if it is very small, is performed after reaching Dasäsvamedhika, the most excellent of all excellent Tirthas,
it is said to be everlasting.
85-86. Holy bath, liberal gifts, Japa,
Homa, Svädhyäya, worship of a deity, offer of twilight prayers,
libation and Sräddha in veneration of the ancestors, everything in
Dasasvamedha is holy. By taking a single bath in Dasäsvamedha Tirtha
and by visiting the Lord of Dasäsvamedha, an excellent man is rid of
all sins.
- On the first day of the bright half of the month of Jyestha, the devotee should take the holy dip in the Dasäsvamedha Tirtha. He is rid
of congenital sins.
- By taking a holy dip in the Rudra Sarovara on the second day of the bright half of Juestha, the sins committed in two births perish
instantaneously.
- An excellent man, taking bath on the days in the following order (i.e. third day, fourth day etc.) till the tenth day m the bright
half of the month shall get rid of the sins of as many births (e.g.
second day—two births, third day— three births, fourth day—four
births etc.).
- On the Dasaharä day that removes the sins of ten births, the devotee should take his holy dip in the Dasäsvamedhika Tirtha. He
shall never experience the torture of Yama.
- By visiting Dasasvamedhesa Linga on the Dasaharä Tithi, one is undoubtedly absolved of sins acquired in the course of ten births.
You can read complete chapter to know significance in great detail.