The Jantar Mantar in Jaipur is an astronomical observation site built in the early 18th century. The Jantar Mantar is the largest of the five such magnificent observatories built in India. It was built by Maharaj Jai Singh II in the 1720s who himself was a great scholar in Astronomy. It was used to measure the distances and positions of celestial objects. The Jantar Mantar of Jaipur houses the world's largest sundial called the 'Samrat Yantra'.
The Jantar Mantar monument consists of 19 large instruments each serving a very specific purpose. It also contains fourteen geometric devices to measure time and track celestial bodies and also observe the planets around the sun. This is the most significant, most comprehensive, and the best preserved of India's historic observatories. It is an expression of the astronomical skills and cosmological concepts of the court of a scholarly prince at the end of the Mughal period. The Jantar Mantar entry fees are INR 50 for Indians and INR 200 for foreign travelers.