Why do we  have to have the Darshan of God , Siva through the horns of Nandi (Bull) in the Siva Temple ( Sivalaya) ?

The Devotees who visited the Lord Parameswara Temple, for having the Darshan they see  Him through the horns of Nandi which is installed at a distance infront of the God, Siva.

There is inner meaning  for it. For every thing in the Vedic Scripts it is elucidated the inner meaning.

Nandi is the Vahanam for the Lord Shiva.  People those who are not aware of the real meaning of why the God has the Ox for his Vahanam (Vehicle).

Nandi is the image of Vedic Dharma, means the Vedas are in the form of Nandi. 

The Horns of Nandi is the symbol for Wisdom (knowledge). In general the Nandi is an  Ox which is animal. The animal has its beastliness which is Pasutwam. So the 

Nandi the symbol for our beastliness (Pasutwam).  But we hold the horns and 

keep our hands on the back side of tail and through the horns we do the darshan

 of Lord Shiva who is in the Garbhaalayam (inner temple) and pray to Him as 

“ O Lord, Siva, I can control my beastliness, I will be good and do the good to all and live virtously. By praying like that and we do have the Darshan of Lord Siva.

More over, as said we are like beasts,  though having knowledge we can have the Athma Samdarshan ourselves. The Horns are like knowledge and the Lord Siva who is inner temple is Athma. Hence we have to have the Darshan of Athma by 

our knowledge.