Jantar Mantar is an astronomical observatory with masonry instruments, built in 1724 by Maharaja Jai Singh II of Jaipur. It houses a huge sundial and other instruments intended to show the movements of the sun, moon etc. This massive salmon colored structure is only a short stroll down Sansad Marg (parliament street). A short stroll down Parliament Street from Connaught Place, is a strange collection of salmon-coloured structures called Jantar Mantar, consisting of several strange looking constructions which are infact very accurately and scientifically devised astronomical instruments for carrying out an organised study of celestial bodies in absence of the telescope. It is also known as the Yantra Mandir. A huge sundial known as the Prince of Dials dominates it. Other instruments plot the course of heavenly bodies, the paths of stars and predict eclipses. It is said that the Moghul Emperor Muhammad Shah had entrusted Maharaja Jai Singh with the task of revising the calendar. Jai Singh made observations for 7 years and built this observatory in 1725. At first sight, the Jantar Mantar appears like a gallery of modern art. Sawai Jai Singh II, a keen astronomer and a noble in the Moghul court, was dissatisfied by the errors of brass and metal astronomical instruments. Under patronage from the emperor, he set on himself the task of correcting the existing astronomical tables and updating the almanac with more reliable instruments. Jantar Mantar contains four chief instruments - The Samrat Yantra - a simple equal hour sun dial. The Ram Yantra determining the position of the sun and also those of moon, planets and stars. The Jai Prakash gives local time, the sun's declination and the zodical sign or group of the stars on the meridian. To the north of the Samrat Yantra is the Misra Yantra, which is a combination of four scientific gadgets.

Largest of the five remarkable observatories made by Jai Singh in five different cities, this is the best-preserved one. It shows the Maharaja s passion for astronomy. Translated into 'Instruments of Measuring the Harmony of the Heavens', Jantar Mantar was built between 1728 and 1734. It is a grand celebration of astronomical science. It appears to be a collection of sculptures with each sculpture serving a specific purpose of measuring attitudes, azimuths, calculating eclipses or counting of stars. This is the only observatory out of five built in running condition. Situated within the City Palace Complex, it is cut off from the main buildings.

Jai Singh was a great admirer of progresses and research made in the fields of science and technology, but he was passionate about astronomy. Before the commencement of construction he sent scholars abroad to study the foreign observatories. The emissaries returned with many manuals on astronomy containing cutting-edge technological information. One of these manuals contained a copy of La Hire's Tables. The king ordered the observatory to be built according to the details contained in the manual and when the construction got over, for the astonishment of the king and others, the observatory was 20 seconds more accurate than the one mentioned in Table. The Jantar Mantar conceived, as a quest for discovering the mysteries of the Cosmos, is a corruption of the Sanskrit word yantra mantra meaning instruments and formulae. It was built not only to verify astronomical observations made at Jaipur, but also to stimulate interest in astronomy. Following the style of an observatory at Samarkand, huge masonry instruments were built, keeping in mind the rules of astronomy, the position of the equator, latitudes and longitudes.

The samrat yantra consists of a massive triangle with a curved structure on both sides. The jaiprakash yantra is a two hemispherical bowl structure representing the celestial spheres and the use of a vertical rod in the center, giving different positions of celestial bodies during the day and night. The ram yantra is in the form of a high cylinder. It is surrounded by circular walls and the shadow of the sun on the vertical and horizontal marble gradations via the cylinder, indicates the altitude and the azimuth or declination of celestial bodies. The composite instrument is heart shaped and includes a sundial and a massive hemisphere on the northern wall. Sawai Jai Singh s attempt to introduce a renaissance in astronomy through Jantar Mantar never took off due to chaos in the country. The first Indian Prime Minister Pandit Jawaharlal Nehru said that so accurate was his work that Jai Singh would have been remarkable anywhere. Thoroughly restored in 1901, the Jantar Mantar was declared a national monument in 1948.

Jantar Mantar is located near the gate of City Palace, Jaipur.