The Beijing Ancient Observatory, known in Chinese as Guanxiangtai, stands on the corner of Jianguomen in the east of the city, directly above the subway station of the same name. It is easy to walk past without noticing: a grey brick tower on a traffic island, with a small courtyard behind a wall. Inside is one of the oldest continuously used observatories in the world.
Five centuries of observation
The platform was built in 1442 during the Ming dynasty as part of a programme of astronomical work, and it operated as an official observatory through the Qing dynasty until 1929. That is close to five hundred years of continuous record-keeping at a single site, which is the reason for its reputation. It is often described as one of the four great historic observatories, alongside Greenwich in London, Paris and Pulkovo in Russia.
The bronze instruments
Eight large bronze astronomical instruments are mounted on the roof terrace, made in the seventeenth and eighteenth centuries. They include an armillary sphere, a celestial globe, a quadrant, a sextant, an altazimuth, and an instrument for measuring ecliptic coordinates. Several were designed with the help of Jesuit missionaries who worked at the Qing court, which is why the instruments combine European mechanical principles with Chinese decorative casting - dragons, clouds and inscriptions in both Chinese and Manchu.
What you can see
The courtyard below holds a small exhibition of earlier Chinese astronomical instruments, star charts, armillary spheres and water clocks, along with explanations of how the calendar was calculated and how eclipses were predicted. The displays are modest but genuinely informative, and most have English labels. Allow about an hour. The instruments themselves are the highlight - they are large, weathered and still precise-looking, and the terrace gives a good view over the rooftops towards the modern skyline.
Practical notes
The observatory is a short walk from Jianguomen station on Lines 1 and 2. It is open daily except Mondays, with a small entrance fee. Because the site is compact, it combines well with the nearby Ming city wall remains, the National Museum of China, or the Silk Street market, all of which are within a couple of subway stops.
