Maharaja Jai Singh II built five Jantar Mantars in different cities across India, including Delhi, Jaipur, Ujjain, Varanasi, and Mathura.

Ancient Indian observatories were primarily used for timekeeping and astronomical observations to create accurate calendars and predict celestial events.

The Samrat Yantra is a large sundial located at the Jantar Mantar in Delhi. It is one of the largest sundials in the world and was used to measure time accurately.

The Ujjain Observatory was an important astronomical center in ancient India. It was located in the city of Ujjain, which was a major center of learning and astronomy.

Aryabhata was an ancient Indian astronomer and mathematician who developed the Surya Siddhanta, a treatise on astronomy that contained important astronomical calculations and theories.

The Nalanda Observatory was an important astronomical center in ancient India. It was located in the city of Nalanda, which was a major center of learning and astronomy.

Varahamihira was an ancient Indian astronomer and mathematician who developed the Pancha Siddhantika, a treatise on astronomy that contained important astronomical calculations and theories.

The Takshashila Observatory was an important astronomical center in ancient India. It was located in the city of Takshashila, which was a major center of learning and astronomy.

Bhaskara II was an ancient Indian astronomer and mathematician who developed the Siddhanta Shiromani, a treatise on astronomy that contained important astronomical calculations and theories.

The Varanasi Observatory was an important astronomical center in ancient India. It was located in the city of Varanasi, which was a major center of learning and astronomy.

Varahamihira was an ancient Indian astronomer and mathematician who developed the Brihat Samhita, a treatise on astronomy that contained important astronomical calculations and theories.

The Mathura Observatory was an important astronomical center in ancient India. It was located in the city of Mathura, which was a major center of learning and astronomy.

Bhaskara II was an ancient Indian astronomer and mathematician who developed the Lilavati, a treatise on mathematics that contained important mathematical calculations and theories.

The Pataliputra Observatory was an important astronomical center in ancient India. It was located in the city of Pataliputra, which was a major center of learning and astronomy.

Lagadha was an ancient Indian astronomer and mathematician who developed the Karanapaddhati, a treatise on astronomy that contained important astronomical calculations and theories.