NEW DELHI, July 20 — Thirteen architectural astronomical instruments, designed for naked-eye observation, sit 723 feet above sea level at Jantar Mantar in New Delhi, an open-air observatory completed in 1724 by Maharaja Sawai Jai Singh II of Jaipur. The site is one of five such observatories built by Jai Singh, with the others located in Ujjain, Mathura, Varanasi, and Jaipur. According to historical records, the term “Jantar Mantar” translates to “instruments for measuring the harmony of the heavens.”
Purpose and Construction
The primary purpose of the observatory was to compile astronomical tables and predict the movements of the Sun, Moon, and planets. Jai Singh built the observatories from 1723 onwards to revise the calendar and astronomical tables. A plaque fixed on one of the structures in 1910 mistakenly dates the complex to 1710, but later research suggests 1724 as the actual year of construction.
By the time of the 1857 uprising, the Delhi observatory had decayed considerably. It was restored in 1901.
The Four Main Instruments
The four distinct instruments within the observatory are the Samrat Yantra, the Jaya Prakash Yantra, the Rama Yantra, and the Misra Yantra. The Samrat Yantra is a giant triangle that functions as an equal hour sundial. It is considered the world’s largest sundial.
The Jaya Prakash Yantra consists of hollowed out hemispheres with markings on their concave surfaces, with crosswires stretched between points on their rim. The Rama Yantra comprises two large cylinders, while the Misra Yantra is a composite of five instruments designed for determining the longest and shortest days of the year.
A Site of Dual Purpose
Over the centuries, Jantar Mantar has also become a prominent public space for protests and demonstrations, symbolizing dissent in India. This dual role — as a precision astronomical installation and as a gathering place for political expression — adds a layer of significance to the site beyond its original 18th-century function. By 1867, when India was under British rule, the observatory had undergone considerable decay.
The restoration in 1901 preserved the instruments for continued use and study. Jai Singh built the Delhi observatory as the first of his five astronomical complexes.
The others are in Ujjain, Mathura, Varanasi, and Jaipur. Of these, the Jaipur observatory had also deteriorated by the end of the 19th century until restoration efforts began in 1901. The Delhi site, now a protected monument, continues to draw visitors interested in both its scientific heritage and its role in India’s civic life.
Observers looking ahead will watch how authorities balance preservation of the instruments’ astronomical function with the site’s ongoing use as a public forum.
