Dwajasthamba Tiruvananthapuram.

this a fine log of teak 80ft in height, circular tapering to the top. this log is covered with series of copper plate rings which are gilded thickly with fine gold on the exterior this is achieved by a peculiar process. The superior kind of gold is used to achieve this first the gold is beaten into plates of the thickness of paper and then cut into pieces which is ground on a stone with sand and quick silver the resultant past is then used to cover the copper rings which when polished and finally heated the sand and quick silver disappear and the gold shines giving the very special effect.

Stala Purana 

It is said that a Bilwa mangala Samiyar used to perform his daily pooja to a few saligramas which he had and invariabaly every day a small child used to interrupt him by displacing the saligrama or the flowers used. One day however the samiyar got angered with the child and hit him. the child felt hurt and told the Samiyar that he was none other than the god he was worshiping but now he was going away to ananthankadu and if the samiyar wished to see him he should come there. on realising the samiyar ran in the direction in which the child had run off but he could here only the jingilling of the anklet and waist band bells he searched but alas. he could only hear the jingaling noice which he followed. One day he heard a small child cry and became alert the mother of the child a pulaya woman was trying her best to quiet the child but it continued to cry she then threatened the child if he continued to cry she would throw him into the Ananthankadu. when he enquired where it was the woman showed him the direction and as he approached it he did hear the same sound of ankletbells and waist band. his joy knew no bounds. suddenly a huge Iluppa tree came falling down with a great big thud. the samiyar saw the figure of Vishnu lying on the adhisesha with his four arms in an endearing pose but the idol was very long they say extending from Thiruvallar to Thirupapur with only the mid portion in Thiruvanantha puram. He fell at the lords feet and sought forgiveness. he also asked the lord to contract himself so that he could offer worship. the Good Lord did so. this idol was worshipped for a long time until it was replaced by the present idol made of 1008 saligramams.