The Kailash Temple in Ellora, Maharashtra, is believed to be the oldest astronomical observatory in India, dating back to the 8th century CE.

Maharaja Jai Singh II, the ruler of Jaipur, built five Jantar Mantar observatories in the 18th century CE, including the one in Jaipur, which is a UNESCO World Heritage Site.

The Jantar Mantar observatories were used for a variety of purposes, including measuring time, observing the stars and planets, and predicting eclipses.

There are five Jantar Mantar observatories in India, located in Jaipur, Delhi, Ujjain, and Mathura. Varanasi does not have a Jantar Mantar observatory.

The Sun Temple at Konark is unique because it is built in the shape of a chariot, dedicated to the Sun god, and is a UNESCO World Heritage Site.

The Taj Mahal is not a UNESCO World Heritage Site, while the Jantar Mantar, Jaipur, Sun Temple, Konark, and Brihadeeswarar Temple, Thanjavur are all UNESCO World Heritage Sites.

The Brihadeeswarar Temple in Thanjavur is significant because it is the tallest temple in India, dedicated to Lord Shiva, and is a UNESCO World Heritage Site.

The compass is not an ancient astronomical instrument, while the astrolabe, sundial, and telescope are all ancient astronomical instruments.

Ancient observatories provide insights into the scientific knowledge, cultural and religious beliefs, and architectural skills of ancient Indians.

Preserving and protecting the cultural heritage associated with observatories in India requires promoting awareness, implementing conservation efforts, and encouraging responsible tourism.