Overview
Vaikuntha (Sanskrit: वैकुण्ठ, Vaikuṇṭha, meaning 'without anxiety' or 'without imperfections'), also known as Vishnuloka, is described in the Vaishnava tradition of Hinduism as the abode of Vishnu, the supreme deity of the tradition, along with his consort Lakshmi. It is regarded as a divine, imperishable realm and the destination of devotees of Vishnu upon attaining liberation.
According to the philosopher Ramanuja, Vaikuntha is the Parama Padam or Nitya Vibhuti, an eternal heavenly realm that constitutes God's abode. In Vaishnava literature, it is placed above the fourteen lokas or worlds enumerated in traditional cosmology, and is held to be the highest of all realms.
Textual descriptions present Vaikuntha as a realm of golden palaces and hanging gardens bearing fragrant fruits and flowers. Its gates are guarded by the twin dvarapalakas, Jaya and Vijaya, while the celestial army stationed there is led by Vishvaksena, the commander of Vishnu's forces. The planets of Vaikuntha are said in the Puranas to lie far above Satyaloka, the highest of the material worlds, though this measure is not understood as a physical distance.
In most extant Puranas and Vaishnava traditions, Vaikuntha is situated in the direction of the Makara rashi, corresponding to the constellation Capricorn. One strand of this cosmological imagery describes Vishnu's eye as being present at the south celestial pole, from where he is said to watch over the cosmos.
References
Adapted from the English Wikipedia article on Vaikuntha.