Explanation: Jantar Mantar is an astronomical observatory built in the 18th century by Maharaja Sawai Jai Singh II of Jaipur. It is a significant example of the scientific and architectural achievements of the Rajput era. The observatory is located in Jaipur, Rajasthan, and was constructed between 1724 and 1734. Sawai Jai Singh II was a keen astronomer and mathematician who was interested in improving the accuracy of astronomical observations and calculations.
Jantar Mantar consists of a collection of architectural astronomical instruments, each designed to perform specific astronomical functions. These instruments include the Samrat Yantra, which is a large sundial used to measure time, the Jai Prakash, which is used to determine the position of celestial bodies, and the Ram Yantra, which is used to measure the altitude and azimuth of celestial bodies. The observatory also includes instruments for predicting eclipses and tracking the movement of planets.
The construction of Jantar Mantar was part of a larger project initiated by Sawai Jai Singh II to build five observatories across India. The other observatories were built in Delhi, Ujjain, Mathura, and Varanasi. These observatories were designed to improve the accuracy of astronomical observations and to provide a better understanding of celestial phenomena.
Jantar Mantar is not only an astronomical observatory but also a significant architectural landmark. The instruments are made of stone and metal and are designed to be both functional and aesthetically pleasing. The observatory is a testament to the scientific and architectural achievements of the Rajput era and continues to be a popular tourist attraction and a symbol of India's rich scientific heritage.
In conclusion, Jantar Mantar is the correct answer as it is the astronomical observatory built in the 18th century by Sawai Jai Singh II of Rajasthan. It is a unique and significant example of the scientific and architectural achievements of the Rajput era, and it continues to be an important historical and cultural landmark in India.