The Archaeological Sites and Remains Act, 1958 defines an "Ancient Monument" as follows:
Ancient Monument means any structure, erection or monument, or any tumulus or place of interment, or any cave, rock-sculpture, inscription or monolith which is of historical, archaeological or artistic interest and which has been in existence for not less than 100 years
A monument or a site is declared to be of National Importance by the Archaeological Survey of India provided it meets the following requirements:
• The monument or archaeological site is not less than 100 years old.
• It has special historical, archaeological or artistic interest, making it worthy of declaration as of national importance.
• It qualifies under specified provisions of definition of the Ancient Monuments and Archaeological Sites and Remains Act, 1958.
• The interested public do not have major objections to such declaration.
• The authenticity and integrity of the ancient monument or archaeological site and remains have not been damaged.
• It is free from major encumbrances.
The central government maintains national monuments, while the state government maintains state monuments.
Vishnu Temple, Vishnugudi, District Wayanad, Kerala was declared as a monument of National Importance. The total number of centrally protected monuments in the country is now 3686.