The idols of Lord Tirupati, Lord Badrinath and Lord Hrishikesh Narayan are carved out of the same Shaligram rock. In Badrik dham Lord Narayan lives alone and here also the four-armed idol made from the black Shaligram rock is alone.
The temple was constructed with big stones. Its walls are 7' to 8' feet wide. The 5' high idol of Hrishikesh Narayan is made of a single piece of black Shaligram stone. Beside it, lies the idol of Lord Varah in a piece of rock.
The outer structure of the temple was reconstructed by Maharaja Yashwant Singh Malvendra Bahadur of Nabha state in 1832 A.D. (1889 samvat). The top of the dome of the temple is made of a single piece of rock which weighs 125 tonnes. There are sixteen corners in the main temple. The outer structure has nine domes which stand in three's in a line.
As is the tradition of the temple, only a few selected renounced seekers, sadhakas, learned scholars and pundits after having a holy bath & purification of body Angnyas are allowed to enter the sanctum sanctorum in the interior of the shrine. The edict in Pali/Prakrit language inscribed in the Parikarma of Lord Narayan indicates that a certain king renovated the temple even before the twelfth century. According to the archaelogists, the original temple is older than Shankaracharya. The pieces of rocks used in the construction of the temple also testify this as they are worn out by the storms and showers for several centuries. The temple is built on a raised platform to protect it from the floods which implies the river Ganga flowed quite near by the temple in the past.
The excavation work done by the archeological department of the Garhwal University found bricks and earthern pots underground which also testify it. The banyan tree in front of the main gate of the temple is also very old.
The idol of Sun God in the temple indicates that it was prevalent in the Shak period. The last Shakya king Rudradev was defeated by Chandra Gupta-II in third century therefore this idol indicates that the temple existed in two or three century B.C.
In the beginning of the 9th century at the time of the renovation of the temple Guru Adi Shankaracharya installed the Sriyantra at the sanctum sanctorium in the interior dome of the temple above the idol of Lord Hrishikesh Narayana in order to harmonise a synthesis of five Vedic rituals and methods of worship between Shaiv, Shakta, Vaishnav, Ganapatya and Saur. The holy installation of Sriyantra was performed with distinct and mystical rituals and was meant for few selected Sadhakas for their spiritual upliftment.
This Sriyantra is worshipped and glorified by various Sampradayas (sects), Shaivs and Vaishnavs. This Sriyantra is very grand and splendid and bestows all powers, success and prosperity. It has also added to the spiritual grandeur and mystical power to this ancient shrine.