Lord Shiva's favourite place is said to be the city of Kashi.
But what are the reasons?
Why Lord Mahadeva likes Kashi but not other places?
Chapter 22 Kotirudrasamhita of Shiva Purana says Shiva himself created the city of Kasi first in the cosmic plane and then brought it to earth for liberating people.
" Whatever things are visible on earth as substantive, as an entity in the form of knowledge or bliss, are eternal, free from blemish, desired for a second. That second, of the tree of salvation, was possessed of attributes and is called Śiva. It splits into two- the male and the female forms. The male is known as Siva, while the female is shown as Sakti. O Excellent ascetics, the invisible Cita and Ananda created Purusa and Prakrti, O Brāhmanas, on seeing their parents, both Purusa and Prakrti developed a doubt. Thereafter a divine voice emerged out from the great Atman free from attributes, “You perform penance, for the generation of the excellent creation.”
Then Prakrti and Purusa said, “O Lord Śiva, there is no place for the performing of tapas. Where shall we perform tapas at your command.Thereafter a beautiful city was built, which was the essence of the lustre and was spread in five kosas and was quite beautiful in which all the amenities could be found. Siva built the city while remaining in the sky in the firmament near the Purusa.
Visnu having been lodged in that city, became desirous of starting creation. He performed tapas sitting in meditation. Because of his efforts, several streams of water emerged from that place. At that point of time, nothing was visible there. Then Visnu saw as to what was the surprising thing found there? Then he shook his head. Then a gem emerging out of his ear fell on the ground, which was turned into a great place of pilgrimage known as Manikarnikā. When the said Manikarnikā in the form of water kept on flowing upto five kosas (Pañcakosi), then Siva held it over the tip of his trident, Then lord Visnu slept there with his wife Prakrti. At the command of Śiva, Brahmā was born out of the navel of Visnu, seated over a lotus. At the command of Śiva, he indulged into a surprising type of creation. He created fourteen lokas around the globe. The size of the globe has been described by the sages to be fifty crores of yojanas.
The living beings in the globe are bound by their karmas and as such, how could they achieve me?” Thus thinking he separated Pañcakos. The region of Pañcakoší, bestows welfare and is the destroyer of the evil karmas, Kāśī, illuminates the path of moksa, bestower of the divine knowledge, and is quite dear to me, Lord Śiva, the supreme soul, there, had been consecrated as a Sivalinga known by the name of Avimukta and spoke, “You have been formed of my amsa as Jyotirlinga and therefore, you never leave this place.” Thus speaking lord Śiva, grounded Kāši, with the tip of his trident and established it on earth.
Even after the completion of a divine day of Brahmā, the city of Kāšî does not get destroyed. O Sages, at that point of time, Sivaholds it over the tip of his trident. O Brähmanas, then Brahmā again recreates the universe, then he again establishes Kāśī. Because of the bondages of the karmas and their attraction thereto, it is called Kāši. The Avimukteśvara linga of Kāśī always remains stable. It bestows salvation to the grave sinners.
There are many places which are dear to Shiva and Kasi is more dear to him, as said by Shiva above. However, this is the legend behind city of Kashi.
There are many holy places of Siva according to Siva Purana. Kasi is only one of them.
3.The Lord has Himself raised up these temples and holy centres in different places for the liberation of the residents of these localities. 4. These temples whether self-risen or not, in view of their being accepted (as their frequent resort) by the sages and Devas are intended for the redemption of the people. 5. In these holy centres and temples, ablutions, charitable gifts, Japas must be regularly performed. Otherwise men are sure to be affected by ailments, penury, dumbness etc. 6. If a man dies anywhere in the Bharatvarsa he shall be reborn again as a man if he has resided in a holy centre where there is a self-risen linga emblem of Siva. ..... 9. The holy river Sarasvati is said to have sixty mouths or holy centres on its banks. Hence an intelligent man must stay on its banks. He shall attain Brahma's region gradually. 10-11. The river Ganga flowing from the Himalaya mountains is very holy with its hundred mouths. There are many holy centres on its banks such as Kasi etc........ 12-13. By ablutions therein and observing fast the devotee shall attain the region of the god Ganesa. The holy river Narmada is a great river of twenty-four mouths. By a dip therein and residing on its banks the devotee shall attain the region of Visnu. The river Tamasa is of twelve mouths and Reva has ten mouths. 14. Godavari is very holy and it quells the sins of murdering a Brahmin or slaughtering a cow. It is said to have twenty-one mouths and accords Rudraloka.
Siva Purana, Vidyesvarasamhita, Chapter 12, 3-14