There were 13 theertha or holy water in Thirunallar, sthala for saneeswar. Now only few of them is available.
Nala theertha - King Nala took bath
Brahma theertha - Brahma used his weapon (thandayutha) to create this theertha and using this he prayed lord shiva
Saraswathi theertha - God saraswathi prayed lord shiva using this holy theertha
Agasthiar theertha - Siddhar Agasthiar prayed lord shiva
Amsa theertham - Thevar and munivar used this
For those going to thirunallaru must take bath in nala theertha and pray nala and lord vinayaga
Vaikasi punarpoosam nakshatra is good time to visit the temple