Jyothirlinga

The Jyotirlingas are sacred sites of worship of Lord Shiva where Shiva Himself appeared as a shaft of light and gave blessings to his devotees, and where His divine presence is alive eternally. This is symbolised by naturally formed Shiva lingas at these temples called jyotirlingas. These shrines are some of the most sacred sites in all the land.

References

http://nithyanandatimes.org/kashi-the-city-of-moksha/