When Sir John Malcolm visited Maraga, he traced distinctly the foundations of the Observatory, constructed in the 13th century, for Naser-ood-Deen, the favourite philosopher of the Tartar prince, Hoolakoo, the grandson of Ghenghiz, who, in this locality relaxed from his warlike toils, and assembled round him men of the first genius of the age, who have commemorated his love of science, and given him more fame as its munificent patron, than he acquired by all his conquests.

In this observatory there was, according to one of the best Mahomedan works, a species of apparatus to represent the celestial sphere, with the signs of the zodiac, the conjunctions, transits, and revolutions of the heavenly bodies. Through a perforation in the dome, the rays of the sun were admitted, so as to strike upon certain lines on the pavement in a way to indicate, in degrees and minutes, the altitude and declination of that luminary during every season, and to mark the time and hour of the day throughout the year. The Observatory was further supplied with a map of the terrestrial globe, in all its climates or zones, exhibiting the several regions of the habitable world, as well as a general outline of the ocean, with the numerous islands contained in its bosom; and, according to the Mahomedan author, all these were so perspicuously arranged and delineated, as at once to remove, by the clearest demonstration, every doubt from the mind of the student.