Beside the concrete knot that is the intersection between Jianguomennei Dajie and the Second Ring Road, the Ancient Observatory, an unexpected survivor marooned amid the high-rises, comes as a delightful surprise. The first observatory on the site was founded in the thirteenth century on the orders of Kublai Khan; the astronomers were commissioned to reform the inaccurate calendar then in use. Subsequently the observatory was staffed by Muslim scientists, as medieval Islamic science enjoyed pre-eminence, but, strangely, in the early seventeenth century it was placed in the hands of Jesuit missionaries. Led by one Matteo Ricci, they proceeded to astonish the emperor and his subjects by making a series of precise astronomical forecasts. The Jesuits re-equipped the observatory and remained in charge until the 1830s.