World Heritage Day is an annual event celebrated on April 18. This day aims to protect all the heritage and recognize the efforts of all the relevant organization working in the field. In 1982, the International Council on Monuments and Sites (ICOMOS) has published the day (18 April) as the "World Heritage Day". The day was approved by the General Assembly of UNESCO in 1983. The aim to establish this day was to enhance awareness of the importance of the cultural heritage of humankind and increase efforts to protect and preserve the human heritage.

At present, Italy leads with 53 sites followed by China with 52 sites. In India, there are 36 sites that have been declared as World Heritage. From Kaziranga in Assam to the Valley of Flowers National Parks in Uttarakhand, India has a range of parks, monuments, wildlife sanctuaries, religious structures and mountains in the list.
As the information given by DD news, here let's have a look at the list of the 36 Indian Heritages those who are declared as a World Heritage:

Cultural
-Agra Fort (1983)
-Ajanta Caves (1983)
-Archaeological Site of Nalanda Mahavihara (Nalanda University) at ---------Nalanda, Bihar(2016)
-Buddhist Monuments at Sanchi (1989)
-Champaner-Pavagadh Archaeological Park (2004)
-Chhatrapati Shivaji Terminus (formerly Victoria Terminus) (2004)
-Churches and Convents of Goa (1986)
-Elephanta Caves (1987)
-Ellora Caves (1983)
-Fatehpur Sikri (1986)
-Great Living Chola Temples (1987,2004)
-Group of Monuments at Hampi (1986)
-Group of Monuments at Mahabalipuram (1984)
-Group of Monuments at Pattadakal (1987)
-Hill Forts of Rajasthan (2013)
-Historic City of Ahmadabad (2017)
-Humayun's Tomb, Delhi (1993)
-Khajuraho Group of Monuments (1986)
-Mahabodhi Temple Complex at Bodh Gaya (2002)
-Mountain Railways of India (1999,2005,2008)
-Qutb Minar and its Monuments, Delhi (1993)
-Rani-ki-Vav (the Queen’s Stepwell) at Patan, Gujarat (2014)
-Red Fort Complex (2007)
-Rock Shelters of Bhimbetka (2003)
-Sun Temple, Konârak (1984)
-Taj Mahal (1983)
-The Architectural Work of Le Corbusier, an Outstanding Contribution to the -Modern Movement (2016)
-The Jantar Mantar, Jaipur (2010)
 

*Natural
-Great Himalayan National Park Conservation Area (2014)
-Kaziranga National Park (1985)
-Keoladeo National Park (1985)
-Manas Wildlife Sanctuary (1985)
-Nanda Devi and Valley of Flowers National Parks (1988,2005)
-Sundarbans National Park (1987)
-Western Ghats (2012)

*Both Natural and cultural
-Khangchendzonga National Park (2016)