This is not a story of mere stones. You will probably have noticed some of the numbered posts along the 103 km border between France and Geneva. Of the 440 in total, 188 of them mark the border with the department of the Ain. They were erected after the 1814-1816 congress and treaties that resulted in Geneva becoming part of the Swiss Confederation and defined the territory of the new Canton. They are noteworthy in terms of both their size and the presence of engravings indicating the direction of the next and previous posts. The border is also marked by other unexceptional posts, simple pegs in the ground and watercourses. 

With its unique location straddling two countries, CERN’s main site is home to three of the more exceptional border posts, numbered 124, 125 and 126. On Wednesday, 28 November, post No. 126, which had been removed while work was carried out on the car park of Restaurant No. 2, was returned to its original place. This was a more delicate feat than you might imagine as the post had to be positioned and oriented to within an accuracy of one centimetre. The operation was planned and supervised by an engineer from the Direction de l'information du territoire de Genève, Geneva’s land registry office, using a special surveying instrument known as a tacheometer. It was important that the post be turned to face exactly the right direction as the engraving on the top must correctly indicate the curve of the border.

The history of the border posts has common threads with CERN’s own history. Built on the periphery of the Canton of Geneva in the 1950s, the Laboratory soon found itself pushed for space. As it was impossible to find room to expand in the communes of Satigny or Meyrin, Switzerland and France signed an agreement in 1965 to extend the site onto French territory and thus allow the construction of the world's first proton-proton collider, the Intersecting Storage Rings (ISR), commissioned in 1971. As a result, the border posts were situated within the CERN site. A further twist in the tale occurred when the PS Booster was built. Commissioned in 1972, the small ring measuring 150 metres in circumference was constructed on the border and covered over; finding itself directly beneath the border, it became the world’s first cross-border accelerator. Border post No. 125, which was originally located above ground, was kept at the bottom of a shaft and remains there to this day. You are therefore unlikely to see it, while post No. 124 is easy to spot on the grass strip above the PS, between Buildings 271 and 365.

As an interesting historical footnote, the border posts installed along the border with the Pays de Gex soon after the 1816 agreement are dated 1818 and bear a fleur-de-lis on the side facing France and a “G” on the side facing Geneva. However, those that have been replaced over time bear the letter “S” for Switzerland on the side facing Geneva, and the side facing France bears the letter “F” instead of the fleur-de-lis, a symbol of royalty. Along the border with Haute-Savoie, the French side of the original posts still standing bears an “S”, reflecting the fact that the territory belonged to the Kingdom of Sardinia in 1816, while the posts that have been replaced in more recent times have an “S” on the Swiss side. All very confusing! The final irony in the story is that the roads running along the border on the CERN site are named after a British man and an American, Ernest Rutherford and Richard Feynman, proving the point that science knows no borders and makes no distinction between nationalities.