Vaikunta (Sanskrit वैकुण्ठम्) or Paramapadham is the abode of Lord Vishnu. It is the place of eternal bliss, exclusive to the Lord, his eternal consort Lakshmi, and the three-folded serpent Sesha Naga, upon whom the Lord and his wife rest.
It is also the name of a three headed Image of Lord Vishnu, where one head is a Lion Head (Narasimha-Avatara) one (the central) is human and one is the head of a boar (Varaha-Avatara).
Dictionary of Hindu Lore and Legend (ISBN 0-500-51088-1) by Anna Dallapiccola
On the Symbolism of Three- and Four-Faced Vishnu Images: A Reconsideration of Evidence. by Adalbert J. Gail, In: Artibus Asiae, Vol. 44, No. 4. (1983), pp. 297-307. p. 298-99