Kalahasti is located near the pilgrimage town of Tirupati and is visited by thousands of pilgrims. This temple is also associated with Rahu and Ketu, (of the nine grahams or celestial bodies in the Indian astrological scheme). Sri Kalahasti Temple is also famous for performing Sarpadosha Rahu,Ketu .People come here and perform pujain for 'Kala Sarpa Yoga'. In any native's chart, the remaining seven houses are in the clutches of Rahu and Ketu is called Kalasarpa dosha.
Savya Kala Sarpa Dosham: From Rahu to Ketu all the houses are filled it is Savya Kalasarpa Dosham
Sri Gnana Prasoonambika is the consort of the Lord and abhishekams are also performed for her as for Sri Kalahasteeswara.Srikalahasti is a very sacred Kshetram where the Lord Shiva's consort Parvati did penance and gained with his blessings a body hundred times better than her previous heavenly body and learned Panchakshari Mantra to become Gnanaprasunamba

The temple named after Sri ( spider ) Kala ( serpent ) hasti ( elephant) after the three animals, who were ardent devotees of Lord Siva. These three animals attained divinity through worshipping Lord Siva.
The main linga is in the shape of an elephant trunk, with tusks on each side and a figure of a spider at the bottom. If you look at the linga from the top it looks like a snake with five hoods. The spider is call 'Sri,' the snake 'Kala,' and the elephant 'Hasti.' The three names combine together in the name Srikalahasti.
It is said that the spider wove a web above the linga to protect it from the sun and rain. The elephant would get water with its trunk and bath the linga (perform abhisheka) and the snake would also worship the Lord. One day the snake found some bilva leaves and water near the Lord. He thought that someone was trying to harm the Lord, so he surrounded the Lord to protect him. When the elephant came the next day to worship the Lord the snake through he was trying to harm the Lord so he got into his trunk. Unable to handle the pain, the elephant dashed his trunk against the linga killing both the snake and the spider. The elephant also died at this time. Lord Siva being satisfied by their devotion, gave liberation to his three devotees.
The spider was Vishwakarma's (architect of the deva ganas) son Oornanabha. He was replicating Brahma-the creator's job and an annoyed Brahma cursed him to become a spider.
The snake was once cursed by Siva himself.
The elephant was a Deva (Pramadha) cursed by Siva's wife, Parvathi, when he intruded their privacy!
The Siva linga at Srikalahasti is an amalgamation of the three animals.

Once there was a spider which was a great devotee of Lord Shiva, which expressed its devotion by spinning webs in the shape of temple and Mantapams to Lord Siva, Ganesh, Kumaraswamy (Kartik) and Nandi.
The morning dew drops would make the cobwebs look like pearl houses and sunrays on the dew drops would make them shine like rubies. But all this would break and crumble with the blowing of the wind. The spider would connect the broken threads and weave the web all over again.
One day Siva, to test the spider's devotion, burned all the spider webs with the lamp that was shining near His shrine. The enraged spider swallowed the flame and sacrificed its life. Siva, pleased with its unswerving devotion, offered it a boon. And what did the spider ask the God ? To free it from further births!
Siva merged it into Himself. One can still see the spider on the Linga!
Legend of the serpent (kala) and the elephant (hasti)
Once there was a serpent which used to worship the Siva Linga with precious gems. An elephant, also a devotee of Lord Siva, used to bathe in the nearby Swarnamukhi river, push away all the precious gems and worship the linga with leaves and flowers from the forest.
The next day the snake, finding her precious offerings pushed away, gets enraged. It would push away the leaves and flowers and worship the Linga with the precious gems it brought from underground.
Next day the elephant would push away the gems and worship it with leaves and flowers. This continued for a while. One day the snake got upset and kept a watch hiding under the leaves all night, waiting to catch the mischief maker.
The elephant also lost its temper finding her offerings pushed away day after day. One day it came early and was pleased to find the flowers left undistrubted. It went and took bath in the river and brought fresh flowers and leaves for pooja (worship). While the elephant was clearing the previous day's leaves and flowers, the snake got into the elephant's head through its trunk, causing unbearable pain to the elephant. The elephant ran helter-skelter with pain and banged its head to a mountain. His head split and the elephant died. The snake was crushed to death too. Lord Siva took them into his fold.
That is how all the three creatures, accursed to be born on earth, can be seen on the linga at Srikalahasti.

KALAHASTI is a town in the Chittoor District of Andhra, and it is a Railway Station on the Renigunta-Gudur section. It has a temple dedicated to Lord Siva, and is famous throughout Andhra as a sacred place and a place of pilgrimage. This religious centre, which is situated between two steep hills, called Sripuram and Mummidicholapuram, is said to have formed part of Seshasaila or Mount Meru, in the ancient days.
Patala Ganapati is a small underground temple located in the same complex. Pilgrims should make it a point to visit this interesting place. One has to bow down carefully to worship this Ganapati 20 feet below on a very narrow staircase.

Sarpa Dosha Nivarana Mantra
'Anantho Vasukee Seshaha Padmanaabhascha Kambalaha
Sankhapaalo Dhaatharaastraha Takshaka Kaaliyasthatha
Ethaani Navanaamaani Nagaanaam cha
Saayamkaale pateth nityam praathakaale'