One usually doesn’t consider astronomy when thinking of Paris. A pity. A visit to l'Observatoire de Paris, located just south of the Luxembourg gardens will change that.

Founded under Louis XIV, l'Observatoire is a research centre, but one that opens up its wealth of science, history, and architecture to the general public.

Originally founded as the Observatoire Royal, part of l'Académie Royale des Sciences, in 1667, the Observatory has continued to expand through the 20th century. The original main building was designed by Claude Perrault (the brother of writer Charles), with other wings and buildings added as technology and needs evolved. Additionally, two sites outside Paris, in Meudon and Nançay, provide more spacious and less light-polluted spots at which to study the skies. These three sites have been responsible for the major astronomical discoveries made in France since that time, such as François Arago’s new findings about photometry, the measurement of light emissions that stars give and the ability to monitor their evolution over time.

Astronomers at the Observatory actively study planetary systems, the appearance and evolution of galaxies, and interstellar space. Because it is not a museum, a visit to this workplace of scientists and students is all the more engaging. As French campuses go, this one beats them all. And it provides one of the loveliest and most peaceful views of the city. The guided tour (in French) leads through spacious, verdant grounds to show centuries-worth of astronomical technology, including two telescopes from the 19th century: the meridian, which follows the paths of stars crossing the Paris meridian, and the equatorial, which follows stars along a parallel to the equator. More exciting still is Perrault’s original building, erected upon the Paris Meridian, which French astronomers established on June 21, 1667, a summer solstice. This line determined time zones until 1884, when the international community chose to recognize Greenwich’s instead. The Casini room, on the third floor of the Perrault building, is cloven by a brass line embedded in the stone floor. You can stand on this historical axis and imagine seeing all the way to Benin.

The tour is a succession of revelations, but one discovery in particular stands out, especially if you go when the weather is nice. From the inside of the Perrault building, you’re led out to the terrace next to the copper dome. There are certainly higher views of the city affording a better look at Paris’s monuments, but this one is the most intimate. Looking northward, you see the Senate building and beyond to a seemingly still city. From this charming view, you proceed into the dome and a room with a large working refracting telescope, a room that seems, like much of the site, at once modern and elegantly old-fashioned. The wooden base of the dome pivots and the copper cupola opens up. Then you go down a wobbly spiral staircase to see the gears and workings of this rotating floor. Going back out onto the roof, even the view seems less exciting in comparison.

How and When to Go

You can take a guided tour (in French only) of the Observatoire one Saturday a month. €3.5-6. Reservations required: visite.paris@obspm.fr (preferred) or 01 45 07 74 78, Mon. -Fri. from 2pm to 4pm.

Next visits in 2008:
• Historical walk “Four centuries of astronomy at the Observatoire de Paris »:
January 19, February 9, April 5, April 17 at 2pm.
• For kids 7 to 12 year-old (accompanied by an adult):
March 15, June 14, July 12 at 2 pm.
• The Observatoire will be open at night during Les Nuits des Planètes (Planets’ Night) from April 12 to15, 2008. Free.